As the percentage of dumb kids increases in the public schools, the worse the test scores of those schools get.
It's no more complicated than that.
Bingo....you win the prize. However unpopular it is to say it on a conservative forum: bad students make bad schools. Many conservatives have been fooled into thinking that putting lousy, lazy, many times violent students in good schools will make them good students. While I’d like to put in stricter methods and stronger programs in public schools (and get rid of all the lib crapola), there’s very little that can be done for millions of students with IQs in the 70-90 range.