Wanted to add that the bad rap of tracking IMO results from times and or places (Germany is one to this day) that put all the low ability kids in a separate school which then ends up concentrating all kids from risk situations, from low SES backgrounds, with parents living in poverty or being unemployed or uneducated, and second language learner and kids with mild learning disabilities and with major behavioral problems, every one else trying to get the hell out of those schools and make it into the medium ability schools. I think those kinds of schools concentrating a high risk population shouldn't exist, and they have been proven to make every kid even worse of than the would be, the concentration of risk factors obliterating any benefit the targeted instruction might bring.
But won't parents who are able to avoid sending their children to schools with lots of at-risk children? Germany has separate schools based on ability. The U.S. segregates based on house prices.
