It isn't "easy" but it isn't hard either. The best classes I have had are heterogeneous mixes of students across ability levels. You design activities, projects, labs, etc. and team students of various ability levels and students will guide each other. I have taught at both traditional "high level/low level" classes and inclusion settings. I had better results by far in the inclusion school. Students didn't have preconceived notions already if they were dumb or smart, they felt like equals, and weren't afraid to get involved because they were with a "smart" kid.
I personally hate tracking because then the "smart" kids tend to stop pushing themselves and the "dumb" group tends to give up and resign them self to being in the lower track. Then you get teachers that develop self fulfilling prophecies about their lower tracked classes and don't give them the opportunities to grow that they should.
Maslow's hierarchy of needs sets this up perfectly. Makes for really unique, and fun classes. And not only are my test scores higher (which are garbage numbers anyway) but I can tell my students are learning actual real skills that will benefit them regardless of career post high school.
That is the quick version. If you want to know more just ask! I know why you feel that way, at quick glance it may def. appear that separating and focusing on different levels on their own is best, but the data shows otherwise.
I'm with you! My "honors" students tended to be more arrogant and less motivated then my mixed class. I loved those kids I taught them for two subjects and they made ridiculous gains. I taught 8th grade and they went to high school so confident and sure of themselves and now those "low" kids are honors students. I still hang out with some of them everytime I go back in town. My higher kids grew a lot too, but the class just wasn't as fun....plus I had 35 kids in that class