I wouldn't give a kid a lever action in 30-30 or 35. They are heavy SOB'S, the crooked stocks kick much harder than the numbers say they should, they are the most difficult to load, unload, and operate. The most likely to have an unintended discharge with as well.
I wouldn't try to buy a 6 year old one rifle forever. By the time he is 16 he'll want to pick his own. Most likely he won't really want the rifle you pick now.
My top pick would be a RAR youth in 223 or 243. He can add a longer stock as he gets older and still use the gun the rest of his life. 2nd option would be an inexpensive break action in the same calibers.
Save your money and for a HS graduation present let him pick out the one he really wants. IF he even wants to hunt or shoot by then. You never know how things are going to work out.
