Training prey drive out of a dog is nearly impossible. As above, the best/only way to deal with it is to limit the opportunities. I wouldn't assume he'll outgrown it. He might just get better at it and move on to adult chickens, right up until someone shoots him. People have a right to protect their animals.
It’s probably not a good idea to have a dog around baby chicks at any time.
But don’t overcomplicate the issue. It’s the same as anything else - if my dog kept eating something that I didn’t want him to eat - I’d make sure it was kept out of his reach.