As long as he doesn't get baptized.
I got baptized because of 1975. Now, with the whole "the Great Tribulation" is starting again and "Armageddon" is just about here, etc., etc., they will encourage anyone and everyone to get dunked.
Which opens up a whole can of worms if he tries to leave.
Perhaps you can encourage your stepson to look to school and actual school books as a way out of the JWs books. If he has an excuse to study for school he may get out of studying with the JWs. He may find that the restrictions they place on him are way too much and find that school is fun compared to the JWs. I hope.