Stumped a bit
 

4th down and 6 - team A gains 5 yards - so the ball would be turned over on downs - after the play is dead Team B is flagged for piling on (dead ball foul)

Is it 1st down for A or for B?

NCAA: Team B first and 10 after the penalty is marked off. This happened in a game a friend of mine worked last week.

Thanks Texas Aggie -
 

I think I found it and it is the same. My partner and I were debating and he said it isn't turned over on downs until the R gives the signal - I don't think so. Rule 5-1.2b says After 4th down a new series of downs shall be awarded only after considering the effect of any act during the down, except a non-player or USC foul.

I think it is 1st and 10 for B after the 15 yard walkoff

NFHS 2-7=1: A Down is action which starts with a legal snap (beginning a scrimmage down) or when the ball is kicked on a free kick (beginning a free kick down). A down ends when the ball next becomes dead."

The instant 4th down ended, free of penalty (live ball) short of the LTG. the "Series" is over (NFHS 5-2-b). The dead-ball PF (piling on) moves the succeeding spot 15 yards, from where it will be 1st & 10 for the opponent, starting a new series.

Case book 5.1.2.e:
Fourth and 2 on B's 25-yard line. A1 is tackled at the 26, short of the line to gain, and B2 then piles on.

RULING: The referee shall signal a change of possession by signaling first down toward A's goal. The penalty for B2's dead-ball foul is administered and the line-to-gain equipment then set, making it first and 10 for B from its own 13-yard line.

COMMENT: On fourth-down plays, A must get a first down by virtue of the yardage gained, including any yardage or an automatic first down from penalties for player fouls during the down, or it is a new series for B automatically when the down ends unless the down is to be repeated. The penalties for all unsportsmanlike and nonplayer fouls which occur during the down in which a new series is awarded, and dead-ball fouls prior to the subsequent ready-for-play signal, will be administered before the new line to gain is established and the chain and box are set. In all cases it will be first and 10 for A unless it is inside the opponent's 10-yard line. On plays other than on fourth down, A may gain a first down by virtue of the yards gained or from penalty enforcement.

I will go for 'B'