In a T.V. movie last night a guy told a kid he needed a proper grip to throw the ball well. That’s true, but the grip he demonstrated was marginal. I would begin practice fairly often with a grip check. Grip check, More videos are at, Practice Baseball to Win
When teaching kids to throw the grip is the place to start. After the initial introduction is important to review the grip, so do a grip check periodically before the warm up session. This is especially true with younger players where it is prudent to do in before every practice until the message is clear.