I've read about various studies touting the benefits of gender segregation in classes. I just recently read about a book or study that says there were benefits ti racial segregation for Black students.  In the end, I think the most important factor is not the makeup of the class but having teachers who are open to the potential of all their students and know how to encourage them to do their best - that along with the home environment and parents' attitudes.. 

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken