In reply to stp:
There's no GCSE in climbing. The PE GCSE requires pupils to take part in, and show ability in, a variety of sports. Each pupil chooses a small number of sports from a long list of options. Climbing has been one of those options for a long time. Now bouldering is an option too.
Not every school offers every option, it depends on what expertise PE staff have (and occasionally volunteers from other departments).
Hopefully the new syllabi will be better than the old ones. I ran some climbing courses for a school I worked at as a science teacher and the assessment criteria for climbing were a joke. Obviously written by a non-climber.