Our SRC was called SRF for Student Representative Forum, we did alot of leadership things with the school, specifically organising charity events. On a small scale we mostly made changes that students had proposed to us, and we brought to the teachers/principal. The SRF's before us for example had created a multi-form, where our school ended up not needing a uniform, only colour coordination - it was very casual. Our principal was great because as long as we had the plan and it had been discussed/passed a vote, we'd usually be able to implement it. It took dedication though, like early morning breakfast meetings.
The last two years before I left the school we raised money to build a memorial garden to students who had previously passed away, and a quiet place for students to sit who need help coping with stress or depression. This was by far one of the most spiritually rewarding things we did for the community.
A small group of us also went down to the Leadership forum last year held at the Sydney Opera House for student leaders. Among other things, we considered total world domination as a top priority. :3
If you can get together a group of dedicated people with ideas, and atleast one dedicated teacher, you'll definately be able to make your SRC worthwhile.