Were these part of a school uniform?  Could you sell them to students who are still in the high school?

Otherwise, why can you not wear them now?

I always find clever and helpful ideas on the site that had this suggestion for polo shirts:

Super Easy kids pants from mens polo shirt

Tee shirt reconstruction seems to be popular with crafty young people. I have never tried it but there are some books on the subject. Two of them are: Generation T: 108 Ways to Transform a T-Shirt and 99 Ways to Cut, Sew, Trim, and Tie your T-Shirt into Something Special. I am sure some of the ideas could also be done with polo shirts. You could try googling tee shirt reconstruction.

You could also make a quilt with them!

I had a few polos from a job where they were required as part of a uniform.  I carefully picked out the company logo, which left a couple tiny holes where the stitching had been thick.  I applied ripstop to the holes and then attached a small iron-on applique to the same location and had new shirts to wear without advertising.  I imagine you could also use dye to change the color first, esp if they were white.  You could embellish around the collar and/or sleeve edges.

Oooooh, nice ideas!