younger ages: toss, drop, reserve?

[dvtaylor]

From the coach of my 5th/6th grade team (i.e., 12&Under):

-- begin quote --
We had an issue in a match. Player A tossed for an overhand
serve and intentionally let it drop. She then tossed and executed
a good serve. On her next attempt she tossed and let it drop,
then tossed and executed a good serve. The opponent called a
time out and the ref took the opportunity to address me. He said
there is only one drop per service rotation. I questioned the rule
and said that by USAV rules you got one drop per service attempt.
He then said that if she intentionally tossed and dropped a service
attempt that he would call a delay of game penalty. He really took
an attitude about it.
-- end quote --

Was the ref correct and NFHS differs from USAV?

Doug