Article title suggest they were failing but book is saying they're turning out sheep.
I don't agree. The article's comments that it's resulting in the production of well-trained sheep is implicit in how these children are failing, and is a consequence (among others) of this style of parenting. The children are failing to learn a self of sense and are crippled in their own abilities to problem solve. They lack agency, have stunted personal development, and are plagued with crippling psychological traumas. The children are 'sheep' in that they are quite often academically very talented, but they are unequipped to handle independence by being crushed when faced with a lack of support. They are sheep who must be guided and micro-managed in every step, and lose what makes them 'human' in the process. The reason they are failing is not one that can be (in all cases) deduced on a chart of academic success, but one that only becomes clear when examining their own personal cases, how they cope with independence, and their own beliefs (or lack thereof). Perhaps in the book, rather than the article, these are not link
I remember some of the kids in elementary school were already "done" with our entire math book (like 400 pages...) when the rest of the class was only on page 100. Is this the kind of thing they are talking about?
It could be, but isn't necessarily. Helicopter parenting is a term which can be rather broad in the specifics, and isn't always easily identifiable to an external party. If we take it at its broadest, it would be 'overparenting'; a situation where the parent(s)/guardian(s) removes both physical and mental agency from their child to an extreme and harmful degree. Things which in some cases may be a sign of helicopter parenting may not in others. Some primary areas in which helicopter parenting may be prevalent, or extremely harmful, are in relation to academic success (extremely touched upon in the article), the pursuit of the child's hobbies, and the child's socialisation. These may manifest externally, or may merely be present in the domestic environment, and very important can deviate in how 'extreme' they are (it is worth-noting that they are inherently 'pointed', but just how extreme they may be can vary).
Academically, as you've mentioned in the post and as is significantly cited in the article, is perhaps where it can be most visibly seen, and appears to have some of the most crushing implications towards the child. While no parent wishes their child to do poorly in school, helicopter parents may take an extreme approach to ensuring this. Helicopter parents may instil severe and exaggerated consequences of academic failure in their child; they might severely berate, criticise, or punish the child for what they deem to be failure (this could be anything below a C, or anything that prevents the child from being the top of the class), and might use hyperbole to scare the child into performing better ("If you don't get an A, your life is over, you'll never get a job and will be homeless for life"; this might also be done more subtly). On the other side of the scale, they may push the child into exemplary academic performance. They may force the child to participate in numerous study groups, they may examine the child's homework and force it to be redone if it doesn't meet their standards, they may force the child to read ahead and do external reading and question them on it, they might provide multiple additional exercises, or they might (in very extreme cases) begin doing work for the child and submitting it as the child's (this appears to be significantly prominent in college application letters from what I've read). While all of this may seem reasonable in small doses, and can be argued as being the best for the child, it all neglects one thing, the child themself. This style of parenting completely overlooks the child's own position, feelings, and sense of self. By the parents rejecting any form of failure, or forcing the child to exceed expectations, the child is not performing academically because they value the pursuit of knowledge or enjoy what they are doing, they are doing it simply because they are being forced, and fear the reaction of the parents should they fail to do so. They don't wish to succeed because it would give them a sense of accomplishment or pride, nor do they wish to study because of the valuable knowledge it provides, it simply revolves ('helicopter') around the parents, and focuses solely upon what they gain. As an individual goes to college, this may be particularly troublesome. Most parents may suggest courses, or provide some feedback on courses that their child may be considering, but ultimately the child generally weighs the decision themself and is merely advised by others. For those victim to helicopter parents, the child, while may 'pick courses', these 'personal choices' don't boil down to their own personal views on the courses or their own consideration of the consequences of choosing it (they may have thoughts on it, but they might not choose it for themselves), but their parents' views. This may be done by blatant means ("you're picking this course and being an engineer"), more subtle means ("you can't choose that course because we cannot financially support it ourselves" and ignoring that the child can still choose it if they can help support it and provide assistance/advice for doing so if that is what they wish to do), to very subtle means (manipulative tactics, particularly insulting, over-exaggerating consequences of choosing something, and other less direct approaches with the purpose of forcing the child's decision against their own will while simultaneously paying no considerations towards the child's will). Without being able to fail, without the ability to make choices themself (even if they are poor choices), or develop their own understanding of why they are doing what they are doing, the child is crippled in their inability to learn valuable personal lessons and develop as a fully formed individual, lacking their own personal drive and merely navigating the course that is provided, oft-times with severe emotional consequences (particularly if destructive tactics are employed, particularly in relation to emotional manipulation or verbal abuse). As soon as the child exceeds the grasp or cushions that are provided by the parents, the damaged child can be in a very problematic space indeed.
The impact of academic 'helicopter parenting' though can be severely heightened by applying it to social situations, a brand that is much more difficult to capture. The most notable and perhaps simply demonstrable manner in which this comes to fruition is in forcing a hobby(or hobbies) upon a child. While encouraging the child to try new things, and giving them a bit of a push is certainly healthy, it turns toxic when it pays no heed to the child's own feelings towards the hobby; if a child continuously expresses a genuine dislike of a hobby, parents will typically recline and withdraw the child, enquiring about other topics that they may be interested in and pursuing those instead, but helicopter parents may not do this, and force the child to continue pursuing it. This may be furthered by forcing numerous hobbies upon the child, even if they do not enjoy doing so much, don't enjoy hobbies, or they interfere with other activities the child enjoys. This may also not be strictly related to taking on hobbies, however. If the parents are extremely overbearing academically or in hobbies the child enjoys, the child may themselves refuse to participate or withdraw because of their parents' continuous interference. When the same standards of success and failure are applied to hobbies and activities, with many of the same methods employed to enforce these (both direct intervention and more subtle manipulation), it becomes a cruelty and carries many of the same consequences by removing agency from the child, minimising the importance of their own emotions and beliefs, preventing them from developing themself, and forcing a reliance upon their parent(s)/guardian(s) to make decisions for them. Hobbies is one thing, yet it can arise in much more subtle and less externally visible ways too. Social interaction with peers and simplistic tasks can be 'helicoptered'. By enforcing abnormally strict rules upon socialising ('not with these people', 'only between these times', 'only in this area', 'this person WILL be your friend', 'you WILL invite this person over', 'you have to go to their house', 'I'm going to follow up with them/their parents to ensure you did what you said', 'you will tell me exactly what you did after' etc.) and preventing the child's own social development, they may become crippled and isolate themself (not wanting to 'deal' with the restrictions or consequences of interacting with others) or be unable to explore. When warnings become strictly enforced rules, and there are more rules than can be found in a transcript of every holy text which has ever been written, the child never develops an understanding of 'why' these are rules, or considers the impact due to how unreasonable they may be (this is a case-by-case basis obviously), and it can be dangerous once independence is gained. Even helicopter parenting in much more simple tasks can be a dangerous issue. When something as simple as interacting with shopkeepers, spending the child's own money, or travelling on their own (I don't mean, say, fly to a foreign country and then inter-railing followed by a cruise around the world, obviously) is never something allowed by the child, or they are never allowed to perform household tasks (either by being forbidden to do so, the parents always insisting on the parents performing the task, or manipulative tactics such as verbal abuse following the completion of a task and the parent themself doing the task after the child attempted). Being repeatedly patronising, condescending, and/or insincerely complimenting the child, too, can be an issue. By limiting the child's growth in social situations, or forcing them (in excess) upon the child without any consideration of the child's own feelings or beliefs, again, the child never gets to plant the seeds of their social and emotional development, they're sowed for them and then chucked upon hard and infertile ground as soon as independence is gained. The child perseveres while they are forced to persevere, and can then react extremely unpredictability depending upon the child's own ability to rebound from what has been inflicted upon them.
Something that needs to be once again emphasised is that what separates this from 'normal' parenting is the extreme and callous disregard it has for the child. While these are often rationalised as being 'for the child' and may result in the child looking very impressive on paper, it can be absolutely devastating and highly destructive (both internally, as it results in emotional damage, and externally, as it neuters independent thinking and fosters a reliance upon the guiding of others). It's hard to 'put on paper' hard outlines as to what solidly classify as helicopter parenting, but it is important to consider when traits are pronounced, far beyond what could reasonably considered normal, and when parents are the sole driving force behind actions. I hope that may help to provide a greater degree of clarification as to some general 'extreme' behaviour that the article may be referring to, but as you may have noticed, there are a lot of "may"s and "might"s in the post, and it really should be taken to highlight that it is very much something that must be taken at an individual level.
The children you refer to may be forced by the parents, and their parents may be looming over them knitting the path before them and pulling the strings, but it could also be a situation where the children are enthusiastic towards the subject/s and wishes to pursue it/them of their own volition; you really would just need to ask the children and parents.
EDIT:
Slate's teaser line is deceptive, the studies aren't about helicopter parents. The statistics are a general mental health survey, not one that was tied specifically to helicopter parents. The excerpt implies a bit that all parents push their kids too hard these days, but it's not based on recent studies. While I agree with the overall conclusions in that article, the conclusions are based on anecdotes and some professor's opinion piece. That article is an excerpt from a book about how helicopter parenting is bad, so perhaps there is more data in the book, but the excerpt is just stories about some really terrible parents.
I don't think pushing your kids academically and trying to control your kids is anything new. It happened to me when I was a kid, and it sucked. It did more harm than good for me, but I worked things out eventually. But back in the day I called my parents every couple of weeks to say hello and give them updates. But these days with the internet, email and smartphones, it's a lot easier to expect constant updates daily. It's easier for parents to invade their kids lives now.
The bolded is itself stated in the article. The reflection on the 2013 study is that there is a growing mental health crisis which extends across every social and economic level, and stems from a facet of modern American childhood. It suggests that 'helicopter parenting' has a responsibility in this, and then touches upon some (recent: 2010 to 2014) studies which demonstrate a correlation (and it notes explicitly that this doesn't mean causation) between helicopter parenting and mental health and problem solving abilities. While I'm in agreement that it fails to cover a broad range of studies, doesn't lay down specific guidelines as to what classifies as 'helicopter parenting' and doesn't really analyse the data with conclusions that generally stem from a personal belief (although like you I feel that it seems like a valid conclusion in the article; that helicopter parenting is damaging), I don't agree that the studies mentioned are not recent or that the article is primarily anecdotes. It definitely is, as you state, very much an opinion piece however.