Yes it is illegal to fire people just because of their age but it isn't illegal to make their job life so miserable and untenable that they quit or slip up enough that a good excuse can be found to fire them.
By the point that they finally let the TL go she was looking them in the eye and saying "I know what you are trying to do, just get it over with."
Of course they would chide her for her attitude even though they were directly responsible for it.
As to usable experience, every place I've worked has taught me something new.
That is part of what I like about doing signing, there is a lot of problem solving, fixing things, and origami.
But none of that is really going to help much on a resume, folks just look at it and see RETAIL.
If my wife wasn't a teacher (in a strong union with good benefits) we couldn't survive on what I make at Target.
