I think you could also validly say that you felt you needed a change so you went back to school...truthful yet you are not disclosing why.

You could also have been "caring for a sick family member" (you are obviously a member of your own family) adn now that person no longer needs as much of your attention so you are free to return to work.

You are not required to disclose any personal information about yourself, your family or anything else. (like are you married, have kids, etc) An employer may NOT discriminate due to disabilities, either, and you are not required to disclose these things unless it affects your ability to perform certain job functions, i would think (obviously, we could not get hired to unload grocery trucks, for instance, if "lifting boxes up to 50 lbs" was one of the job requirements.

i had not thought about this too much yet, myself. Good question to bring up, thanks!!