The decision to have your child "play-up" is something that requires careful consideration. Such a request is generally made when a player demonstrates a skill level above his/her age of play and when there is a team available. Such a request should be made to the appropriate age group commisioner and requires board approval if the player is requesting to play up more than 1 year.
Two things to note: you need to register your child in their correct age-group, using the Special Request Form to request that they "play-up."  CSA has final approval of any player requesting to "play-up."