“It was not until after [Plaintiff] . . . brought to [employer]’s attention that he had a Texas Teachers Certificate that [employer] reconsidered the propriety of qualifying an instructor based on a Texas Teachers Certificate. At that point, [employer] determined that a Texas Teachers Certificate is not the equivalent of a Bachelor’s degree. The issue is not what qualification standard applied after the alleged discriminatory act but what standard applied at the time it occurred.” El Paso Cmty. Coll. v. Lawler, 349 S.W.3d 81, 87 (Tex. App.—El Paso 2010, no pet.).