How high can a defender tackle?

Under 13 to Under 15 (SafePlay Code): tackles above the armpits are not permitted. It is an infringement if, while attempting to tackle a ball-carrier, a defender makes contact above the armpits intentionally, recklessly or carelessly.

The one stated exception: a defender in front of a ball-carrier who is diving or falling may come into contact with the ball-carrier's shoulder, provided the defender's arm or arms extend down the shoulder and trunk, that is, underneath the ball-carrier.

All ages under the International Laws (including Under 16 to Under 18): it is misconduct to make contact with the head or neck of an opponent intentionally, recklessly or carelessly when effecting or attempting to effect a tackle (Section 15, law 1(b)).

When a player in possession is held upright by two or more defenders, any other defender must make initial contact above the knees (the knee joint).

Sources: National SafePlay Code 6-15 years, https://www.playrugbyleague.com/safety/safeplay/ and the International Laws (April 2023), https://www.playrugbyleague.com/media/14513/nrl-international-rules-book-2023_web-version-1.pdf