Knee savers

If your son had or has a bona fide knee issue (surgery) he might need to use them.  Otherwise, I would recommend tossing them out.

My kid used them when he was 10.  Thought they made him look cool.  Starts up with his catching instructor who asked him if he had knees and why he used them.  Kid took them off right there, never to be seen again.  My own opinion is it may have a tendency to make a kid lazy.  I would go without them if possible. 

I can't recall seeing a HS kid use them.  HS kids like to gear up like the pros. If pros used them, they would too.

FWIW, I coached one year of LL with a dad who was head of sports medicine at the local Kaiser. He said they were horrible for kids' knees and wouldn't let his own kid use them.

At my son's division 3 school occasionally on the fall a cathcer will show up with them.  They usually get rid of them pretty quickly.

Sometimes I see catchers on opposing teams wearing them.

When I train kids who wear them, I do not make them take them off.  Mainly because I think a good intending parent spent money for the betterment of their kid. BUT, I always tell them that they have limited value, and if they choose to use, keep them low.  Sometimes, you will see catchers that wear them higher than the bottom strap, which actually does harm!  The White Sox catcher, Tyler Flowers, actually does this and I want to scream to kids, "do not watch".   

Old catchers with old knees find some relief using Knee savers...but that's about it.

My son used to wear them but found it easier to block without them. Sometimes, if he's catching a double header or planning on a long training session for example, he'll put them on.