Age is the fastest growing form of discrimination, and there is n o t h i n g to be done about it. Very hard to prove----and impossible to prevent, at least on the pre hiring end. 'Oh, we're not allowed to ask your age on the application'. Sure. They just get the info from your s.s. # which is completely legal and necessary to obtain.
Sadly this is the truth and, even more sadly, things will stay this way for a long time. A good post by @XplooZv-rju