My point Platypus is that research shows that there are better and less expensive ways to improve student outcomes than reducing class sizes. Hiring more teachers and opening new schools, especially where the union is all-powerful like in 4J, is extremely expensive. With larger and larger percentages of education dollars going to current salaries/benefits and PERS where is that money going to come from? Charter schools are succeeding all over the country. The obvious elephant in the room is the intractable teacher's union that serves the interests of the teachers at the expense of the students. 

Differentiated instruction is one of the many "smoke and mirrors" tactics of progressive education. So is having the high achievers "teach" the low achievers by putting them in the same classroom for group work. It makes administrators and teachers feel good about themselves (and lightens the workload) but only short-changes the hard-working motivated kids. Been there and seen it many times.