I am a first year official in Arizona.

Working an 8th grade tackle league using Federation rules.

Working as Linejudge.

Play goes to far side.

Right in front of me, about 20 yards across the field from the play, A1 hits B1 in back and knocks him down. I flag it and go to talk to the White Hat after the play. I thought it would either be a block in the back or unnecessary roughness. Penalized it as a block in the back. White hat pulled me aside at half-time and said that it shouldn't have been a foul because A gained no advantage from the action.

Would do you think?

Well he could be right but probaly not. If you believed that the block in the back was a safty issue(which most are) then you should have called it. Anytime a player knocks over another player from behind then I will definitely have a call. If he makes him stumble and clearly no advantage is gained then I probaly would pass on it.

Hope that helps, good luck out there. :)

Agree with what snak-eyes said. This is not an advantage issue, it's a safety issue.

It is a safety issue and must be called. ALSO it is a control of game issue. Players who think that the other team is "getting away" with cheap shots can very often get out of hand behavior wise. I have both the safety issue and the control of the game issue as reasons to flag it.

I totally agree with my esteemed, learned colleagues.

First - I agree with the call. It certainly falls under player safety.

With that said, it is difficult to tell from your description exactly where the foul occurred. Your WH may have been more concerned with the area of the field you were observing than the call itself. When the ball carrier enters the opposite sidezone, you should turn your attention to an area behind the U & BJ (5 man). We should have at least 3 sets of eyes (L, BJ & U) watching that sidezone. Our weak area is now in the middle and deep. You should not see fouls in the opposite sidezone if you are working your area properly.

Unnecessory Roughness?
 

You could call Unnecessory roughness on that play. It's the same as a 'blind-side' block 25 yards away from the ball during a scrimmage kick play.