Have you looked at or tried almond milk or coconut milk. I would be very hesitant about giving soy milk to a pre-adolescent boy due to soy's estrogenic properties. Well I know this is a controversial topic among people. I'm one of those who goes to a doctor who feels "soy products of any sort are not a fit food for humans, especially of the male gender, except as a small condiment, like a splash of soy sauce". But even if you don't believe it why not try something else. I happen to think almond milk and coconut milk are far tastier than soy milk which is another consideration too.