Teens, what do you do with old clothing? ?

All of the above.

if it's gently used and not worn down, i donated mine to goodwill.  

I have four shirts in my closet, two are identical but they are all similar. The other two are different in colour. I wear one of them. The other ones still have the tag i haven’t used them and i bought them in 2017. If a friend comes and wants to take one they can go ahead and take them.