Essays / Counter-Argument against Co-education! [2]

I'm having trouble, coming up for a counter-argument against Co-Education!
Here is what I have so far:

Despite the average perception that single-sexed education benefits students in terms of academic achievement. Studies prove the assumption that "girl's do better in an all girls school and boys do better in an all girls," by a study that was conducted in 2005-2006 by the Strategic Counsel.