Inbounds ruling
 

When a team is inbounding the ball, and they have 4 players stacked together, is the defensive team allowed to step in between the offensive players?

How are they stacked in relation to the applicable line? Parallel or perpendicular?

If by "stacked" you mean perpendicular to the boundary line, then the defense is not allowed in (unless they get there first, of course).

If the offense is parallel to the line and within three feet of the line, then the defense is allowed in.

If the stacking is perpendicular to the boundary line. Offense does not have to allow Defense a spot. If stacking is parallel to boundary line and within 3 feet of that line the defense is entitled to a spot if they want it.
NFHS Rule 7.6.5

And regardless, if the defense gets there first, they're allowed.