They aren't getting a discounted travel ticket, they're getting free bus travel in return for carrying around a photo ID all the time. (I don't agree with fourteen and fifteen year olds being able to travel on the bus for free at ten or eleven at night on Friday or Saturday and getting up to no good on the public coin. It was sold to the public as a school bus replacement and/or reducing car use. It is an obvious attempt to normalise ID cards.)