Can't find the blasted thread again but just in case anyone remembers, thanks for suggesting good causes that would get the whole school involved in some kind of activity.
The school council (kids from each form) has chosen Mary's Meals and their Backpack project, which was an MN suggestion! And something I'd never have heard of without MN.
here for anyone else who is interested
Sorry but being unable to find the thread I can't thank the poster who suggested it - but hope she sees this.
Oh, and it turns out one of the key people involved is an old girl (long enough ago that no-one at school today knew her) so I'm particularly pleased MN helped me find this scheme.