Interference by offensive team

Question
R1 on 2nd base when batter hits ground ball to left field.  Left fielder fields the ball and throws home.  Runner 1 rounds 3rd and heads home.  On deck batter enters home plate area and interferes with play.  I call dead ball, batter interference and return R1 to base last occupied at time of interference.  Was that the correct call?  When does the on deck batter become the batter, when she leaves the on-deck circle or when she enters the box.  NFHS RULING PLEASE.

Answer
First, a player becomes a batter when they enter the batters box in preparation to receive a pitch.  In your situation, the girl that interfered with the play was not a batter.

When a member of the team on offense, player or coach, interferes with the defense, the lead runner is put out and any other runners are returned to the last base touched at the time of interference.