What's with the US and crappy math scores. If it was ranked by the math column, they be maybe middle of the pack tops.
If public education is the same as it was when I was in Jr high and high school (early 90s) then I can tell you why US students are worse.
It's unpopular to be smart. Doing good in school and getting good grades wasn't getting you popularity. It also wasn't getting you laid. Let's face it kids in school are going through puberty that's what is on their minds (I know it was on mine at that age). I remember smoking weed and being a rebel to school made people popular. I was into Ad&d, video games, computers, dirt bike riding and fixing and doing good at school in Jr high. I got picked on and wasn't getting close to getting a date.
In 9th grade some friends had some weed. I tried some while dirt bike riding up on the local resovoir hills. It changed my whole perspective. I started caring more about phsycadelic music, drugs, partying and allmost instantly my popularity soared. I started getting blow jobs by camp fire girls and was getting laid.
In order to do this more often I focused more on work and less on school. This led me to driving and having a car before other kids. Which in turn meant I was up a rung in the dating pool. I seen this with a number of other kids too. It seemed if you weren't into football and were smart you weren't getting tail. If you were smart and doing school work/studying you were picked on for it. Going to concerts, and being into grunge or the greatful dead got you popularity and women. It seemed the only way to do this for a young man who wasn't into football. (My high school was known for its undefeated football team and those kids got away with anything as long as they played football).
My personal story gets bad after that from selling weed and lsd then to using harder drugs and to getting rammed off the road and stabbed in Philedalphia. It took years to get back on track and many downfalls.
I didn't take studying and doing good with things until I was almost thirty. I went to college in 2006 yet graduate hs in 96. Now at 40 ive gone full circle I focus on gaming, and Ad&d again, read books and listen to intellectual podcasts, don't do drugs and was married for 8 years (the bitxh ex wife is now off with a younger dude who is a stoner who doesn't work and has kids from 3 different women and got her pregnant at 41, dude has no job lol)
I bring all this up because some kids are really bright and talented. They suppress it to fit in. Peer pressure is a bitch. Many want to get laid as that's what our culture tells them. If you aren't hooking up with people you are a looser (the incel jab the far left uses). So what do you think many teens will do? Screw studying, school work. Look how many kids in America are smoking weed today openly. Or into all these weird sexual things. Porn has been normalized.
I am sure the kids today not into the same music (instead of Jerry Garcia, Kurt Cobain and Metallica, it's all the rap people and booty pop, Drake, Sixnintierwhatever and CardiB) but still the culture of shunning doing good, partying doing drugs, distancing yourself from your family is all there.
If women in high school dated smart kids instead of football players or ones who were super popular then maybe more guys would get into getting good grades. Now take it this is from a guy's perspective and I'm sure it's different for women but not entirely.
If smart kids were championed in pop culture instead of being degraded maybe the US could rise in the ranks. I don't think kids care enough and they have no reason to, the incentives are all wrong and inverted.
I look back and know I could of done better and scored better on tests, as I was 4.0 GPA in college and earned scholarships when I cleaned up and wasn't chasing the dragon.
My story in anecdotal, but I'm sure there are similar tales of saying fuck it, fuck school and partying instead of studying hard and doing the right thing for your life and family. I learned the hard way.
So if teen age girls go after smart geeky kids instead of jocks or druggies than maybe more kids would go that direction. Pop culture makes doing good in school and being a good son/daughter a bad thing and lame. China doesn't have this problem, instead they are held hostage at gunpoint and don't know any differtly.