Not sure how it could be considered age discrimination though. You tend to forget 'knowledge' like this fairly quickly. I know for my part at least I generally have to brush up on this kind of learning about every six months (or even less perhaps), if I wanted to retain it.
It would be like requiring you to recite all the marks you received on all your assignments in all your classes in your last semester of your senior year of college. I assume that if you had just graduated, this would be easy, but if you had graduated 10 years prior, this would be hard (feasible if you'd kept the paperwork--but hard).
