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.
First of all, how the teams would do against a 5A opponent isn't relevent. Its likely that SLC has as many people participating in athletics as Celina has in their entire school. 2A football teams have about 20-25 players suit up for varsity. SLC has probably 50 or more.
Second, SLC hasn't had a lot of solid division I talent there. There are few, if any, people you can name that came out of SLC that are current major conference all-conference. About the only somewhat big-name player is Garret Hartley of OU, and he's a kicker. Chase Daniel at Mizzou may start there, but he won't be a factor in the Big 12. Other than that, there aren't many DI players out of SLC.
In reality, the largest Texas high schools have over 5,000 students, and two of the biggest: Plano and Plano East, have that many on their campus which is entirely Juniors and Seniors. 2000 is barely enough to make 5A. In fact the cutoff this year was something like 1978.