Yeah, some good players come out of the small schools, and Colt McCoy was something special. But even if you look at the best 2A and 3A schools, like Celina, Crawford, Newton, Boyd, etc., how would they do against teams like Southlake Carroll? Also, it's not just that the teams are better overall, but a school with 250 students might be able to have two or three people competing for a position. Some of the big Texas high schools have 2,000-2500 students, so there's a lot of competition just to get on the field.
I'm not saying he can't do it, just that it's a bigger jump in competition for him than for guys who played in 4A and 5A schools. Of course, he had the redshirt year, so that should help him a lot.