How high are children allowed to tackle?

At every contact age from Under 9 to Under 12, the RFU Rules of Play say:

• The tackler must grip and hold the ball carrier below the base of the sternum (the tummy or belly and below), and the tackle must include the use of the arms.
• Only the ball carrier can be tackled.
• The ball carrier must not go into contact with their shoulders below their hips, dip late and low, or put their head into the opponent's head space.
• Supporting players must not run either side of and close to the ball carrier to block tacklers.

Fending off: not allowed at Under 9 to Under 11. From Under 12, a hand-off is allowed but only below the armpits.

Sanction for a high tackle (contact above the base of the sternum):