How to help my first grade little leaguer hit the baseball?

Might be someething simpler than that. everyone pitches differently and your release is probably easier for him to read and pick up. Also hes hit off you for how long compared to the new coach? Tee might help some but it sounds like he needs to adjust to the coaches release. Could just be nerves as well.

As a baseball player myself i have had my dad pitch to me for years. I still have the tee to keep my hand eye coornation. I think you should just have the coach practice with him more try to have him give a couple of little pointers here and there. It will definitely help. My coach last year was a high school coach and he showed us many different techniques that made us all a lot better.

The only thing that helps with hitting is practice....repetitions. Let him hit off the tee....then kneel across the plate from him and toss balls for him to hit, then go to pitching. I'd even go so far as to let the coach SHOW you his grip on the ball, so maybe you can throw it the same way.

even though the pros have to go out and face 90+ mph pitching they dont practice that as much as tee work it improves hand eye coordination and especially mechanics thats what he needs to work on if he wants to hit the ball more consistantly

Practice, repetition, the more he hits the ball the better he'll be.

Thats the only way to get it done, thats the only science that'll work for him.