The NSWRL has moved to keep children in the sport by introducing 21 weight and age competitions across Sydney that will have major ramifications on participation levels in rugby league.

The initiative has been backed by Penrith halfback Nathan Cleary, who recently told Fairfax Media he wouldn't be playing the sport if it wasn't for the weight and age competition he played while living in New Zealand as a teenager.

Over the next four months the NSWRL will run competitions based on weight rather than age.

Debate over allowing smaller children on the same field as much bigger kids the same age has been rife over the past few years.

But over the next four months the NSWRL will run competitions in the Penrith, Parramatta, Manly, Balmain and Western Suburbs districts that will place emphasis on ensuring children aren't lost to the sport because of a fear of getting hurt.