The Rookie Me Coach system is completely customised to the age you set up your team with.
You will need to delete your team and create a new team, setting the age accordingly to access another level.
Please note, if you do this then any content or settings you have for your current team will be deleted. Or, Alternately;
You can upgrade to premium where you will have access to create up to 3 teams and manage all at the same time. Accessing the multiple curriculums, sessions etc.