You can never ever put too much emphasis on balance and loose. Had a young man spar tonight-15 days into boxing- with a guy with two years. He handled himself well, clearly controlling the rounds.
He had good balance because every day he puts in 3 rounds moving around and watching the mirrors right smart. Good stiff jab and he countered well to the body
It isn't hard to get them up and running. The gym I'm at is a fight gym so the sparring comes quick. But you can get a young man into the ring, with something to work with, pretty quick. Then he has some idea and knows a bit and you now can put things in perspective.
Great teaching tool if you know what counts and know how to get there.