from...
http://www.tfgm.com/journey_planning/tickets_low_fares_under16.cfm?submenuheader=1"From 16 May 2011 if you're aged 11 to 16 you will need an igo pass to pay the concessionary fare on buses in Greater Manchester. An igo pass proves that you are aged 16 or under and is valid until 31 August after your 16th birthday. When you are 11 you need to carry proof of your age to pay the child fare on Metrolink trams. You can use an igo pass to do this.
The igo pass replaces the ID-16 card. If you already have an ID-16 card, you can carry on using it until 15 May 2011 but if you don't have an igo pass after then you will have to pay higher fares."
