I think I should also gently suggest here that the issue could also be expectations. The idea that you put 30 random children in a class and that therefore there
must be some who are "gifted", and there
must be some who are "slow".
I don't know man? I'm just saying that sometimes sure, all the kids in your neighborhood could be above average. But most of the time, all the kids in a class are just average. And now the poor teacher has to explain to irate parents that their kid's not any more special than the other kids in the class. (Only we don't. We acquiesce to their insanity and label average at best kids as "gifted" and then have everyone be shocked when those kids don't gain admission to Ivies. Ma'am, that kid was lucky to get into his/her state flagship. And even at that state flagship, s/he probably ain't gonna be majoring in ChemE or anything if you want my honest opinion.)
Sure, you can have slow kids in a class. But, really? 30 random kids? Is it statistically likely that any are "slow"? Or is it more likely you're dealing with no good parents who don't work with their children at home? Then those same parents come to berate the teachers for not doing enough to teach a fourth grader addition and subtraction. With absolutely no reflection on why a fourth grader, with no learning disability, doesn't understand addition and subtraction.)
I don't envy teachers because these are the attitudes they have to deal with.
Public Service Announcement: No people, your children aren't "gifted". And it's very unlikely that your kids are "slow". Your kids are very likely, (horror of horrors), just average. Every one of them.
If we can just get past those things we can start looking at some of the real issues.