According to new research (pdf) by Spyros Konstantopoulos, the answer is no. Small classes are better across the board, but the thesis that they are relatively more beneficial for kids being left behind doesn't appear to hold. From the paper: "The results consistently indicated that higher-achieving students benefited more from being in small classes in early grades than other students. The findings also indicated that although all types of students benefited from being in small classes, reductions in class size did not reduce the achievement gap between low and high achievers."
Personally, I blame the teacher's unions.
