Incidental Contact:

NFHS Rule 4-27

Incidental contact is contact with an opponent which is permitted, and which does not constitute a foul. 

Art 1… The mere fact that contact occurs does not constitute a foul. When 10 players are moving rapidly in a limited area, some contact is certain to occur.

Art 2… Contact, which may result when opponents are in equally favorable positions to perform normal defensive or offensive movements, should not be considered illegal, even though the contact may be severe. 

Art 3… Contact, which does not hinder the opponent from participating in normal defensive or offensive movements, should be considered incidental. 

Art 4… A player who is screened within the player's visual field is expected to avoid contact with the screener by stopping or going around the screener. In cases of screens outside the visual field, the opponent may make inadvertent contact with the screener, and such contact is to be ruled incidental contact, provided the screener is not displaced if the screener has the ball.

Art 5… If a player approaches an opponent from behind or from a position from which a player has no reasonable chance to play the ball without making contact with the opponent, the responsibility is on the player in the unfavorable position.