It's no secret that some jobs discriminate based on age and gender. There's a reason that restaurants typically have teenage girls work as hostesses and servers and teenage boys washing dishes or bussing tables. It's not because one group is uniquely skilled at one of these jobs but because of industry conventions. There are still incredibly legal ways jobs can discriminate against certain groups. For example, have you ever applied to a job where one of the requirements is “the ability to lift…