Stack on throw-in

[BigCat]

Originally Posted by BryanV21

NFHS - No. Unless you mean the stack is adjacent/parallel with, and within 3 feet of, the line.

I don't know if college is different

End of Rule 7 for nfhs and ncaa. By "stack" I assume you are talking about a line perpendicular to end line or sideline.
Defense is not allowed in. As Bryan said, in high school if players line up parallel/ side by side to the end line within 3 feet of it they have to be let in. ncaa says within 6 feet and parallel they have to be let in. Ncaa actually has provision saying teammates can be adjacent if perpendicular.