I haven't read all the responses to the OP. I'm responding only to the OP's question - how is ability grouping going in public schools that are doing it. We are in a public elementary school in one of the cities listed by the OP. Our school has been ability grouping for reading and math for about six years now, and it's going extremely well, evidenced by test score increases, and student/parent satisfaction. It's one of the main reasons we chose our school (which also happens to be our neighborhood school), and we have long waitlists of students trying to choice in from adjacent elementary school districts.
They take a class of 90 kids and shuffle them among the three grade level teachers, plus ESL and intervention teachers if needed, for reading, and do the same for math, minus the ESL/intervention teachers. They reshuffle the kids throughout the year if they need to based on scores/performance, although our DS's classes have stayed fairly static. The reading classes are further broken into three to five ability groupings within the overall reading class. So my DS, for example, is in the lowest ability reading group in the highest ability reading class.
The high ability 1st grade math class is actually doing higher level math right now than the lowest ability 2nd grade math class. The 2nd grade high ability reading class has readers spanning about 5th to 10th grade level.
The school also still moves very high ability kids to other grades by subject, but typically only if the parents push for it or you happen to get one of the teachers who's really on top of it. I see the effects when I volunteer in the ability-grouped reading class versus the homeroom class - the ability-grouped class is more focused because they don't have as many outliers who are either bored or over-challenged. The ability grouping plus subject acceleration for math is working very well for our DS, and I know a number of parents who have chosen to keep their children at our school rather than move them into the HGT magnet program in our neighborhood.
Our old VP moved to another neighborhood school and started implementing the model there last year. Friends at that school also seem happy with the model. I don't know what other schools in our city are following the model.
