Texas only requires a parent to support their child through the age of majority.  Once a child is old enough to enter college, their support obligation generally ends.  However, the exception is if the parents specifically agreed that one (or both parents) would contribute to the college education of the child.  If you did not get an agreed order at the time of your divorce (or at the time the original custody order if there was no divorce) requiring dad to pay college tuition, then you cannot go back now and force him to do so.  At this point, it is strictly voluntary on his part.