Coarse fish are not eaten in the UK and are always put back. Please don't let him use a keep net, they kill the fish.
Many Eastern Europeans do eat river fish, and this is a point that is causing friction with anglers in the UK.
I hope your son enjoys the hobby. It's not for me, a) maggot drowning and b I hate actually catching the fish. Not really a basis is it? Dad was a very good angler though so I saw a great deal of fishing whilst being told not to upset the fish! Lol