If possible start with a .22 rim fire to teach shooting skills. As for the deer rifle NEF makes a nice little single shot in .243 and Remington makes a model 7 youth in .243, .260 and 7mm-08 ( from what I've read here 7mm-08 would get my vote now but I did start my son with a .243 and use that myself too)Winchester has a youth rifle in .243 and .308. I didn't look lately but I'm betting Savage has a youth rifle too probably .243 anyway maybe some others too.