Held Ball

[DrC.]

I've seen this one handled differently my many of us. Player A1 and B1 jump for a rebound with both players hands on the ball.
Because A1 is either slighlty taller or stronger he brings the ball down in front of him but B1 does not let go. A1 has B1 on his back. Do you call held ball because they both have the ball and initially there was no contact or do you call B1 for a foul because he is now on A1's back. Would you call it differently from a 7th grade game then you might from a JV game ???