If your child is in early French Immersion (Public School board), the congregated gifted class start at grade five. For the English program, the gifted started at grade one. There are only about 3 or 4 schools offer congregated gifted class for grade one to three. Majorty of English program students start at grade four, which more schools have the class.
You should be able to get more info from the learning support teacher of your child's school. Or you can call the board ask more information. The person in charge of this in the school board is Nancy Reid (at least in September). You can call her office go find more.