Free money for your school! Easyfundraising.org.uk
This is something that my parents/sister have been using to raise funds for her trip to the world scout jamboree this year, and is available for just about any charitable group.
Fundraising Ideas | Easyfundraising.org.uk
Almost every major retailer and many others are already on here, and they seem to add more regularly.
Simply, you sign up the school as a cause, and then you make your parents, teachers, neighbours whoever know about it. They can then sign up as an individual, and browse through the retailers list.
Any purchase they make by following the retailers links, earns a donation towards your cause. This ranges from £1 upwards in static donations, or up to 15% depending on the retailer.
It doesn't cost them anything extra, and it doesn't cost you anything.
You can then claim the money back as a cashback donation.
I heavily recommend looking into this site for your school, especially in these financially troubling times!
PS, if you have a cause setup already, then please post here that you can do referrals! This earns the referrer a little extra each time.