I don't know about TX, but in GA, pre-K starts at age 4. There is a state funded program called Head Start for 3 year olds. I encourage you to get him started right away, because if he can learn social skills and focus, he will be on the right path. I bet if you called your nearest school or county school board, they would be able to point you to some education programs that would suit your child. Hope this helps.

Hi Christie,
 
Some pre-K programs do enroll three year olds. Contact those in your local area to find out their enrollment requirements. You may be able to use SchoolFinder to find their contact info:
http://www.education.com/schoolfinder/
 
Here are some additional resources on Education.com you may also find helpful...
 
Preschool Readiness info center
http://www.education.com/topic/preschool-readiness/
 
Another JustAsk Q&A that matches your question exactly:
http://www.education.com/question/age-child-start-pre/
 
Preschool Activities & Worksheets:
http://www.education.com/activity/preschool/
http://www.education.com/worksheets/preschool/
 
I hope you are able to find a great program for your son, and that he continues to do well.