when is inside pick to 2nd a balk?

[davekoch]

11 year-old pitchers under NFHS rules.

while practicing inside pick off moves to 2nd base at our last practice, a few coaches started to wonder about two aspects of when would would it be called a balk; one - where in the rules is the following declared a balk, and two - when would/should umpires call the following a balk: the latest point in the delivery from the set position that the pitcher can turn to second and make a pick without being called for a balk?

from the set position our pitchers do a good job of bringing their free leg straight up to a balance point and then letting it fall straight down before delivering to the plate. some coaches say to pick to second the latest the move can be made is at the balance point, while some said the latest was after the leg dropped back down from the balance point as long as he didn't move toward the plate, but dropped and moved to second.

i have the 2003 NFHS rules and can't find anything that specifically addresses this point and wanted to get some expert opinions.

thanks for any insight,
-dave, just a coach