We dont have an animal rights group at my school, but we DO have an Interact Club, which is sorta like a community service group where we just host a tonne of fundraisers & events throughout the year.
This year I won a leadership possition in Interact and have kinda steered the whole team into an animal-advocacy direction. For example, we are hosting a fundraising festival at our school on Monday where we are selling Animals Australia merch, 'cruelty-free' cupcakes, showbags and running an assortment of other competitions for the littlies.
Other suggestions:
-A bake sale (food is NEVER out of demand)
-Casual clothes day (our Interact club has this planned for our first event next year. we are predicting a success seeing as our school has never had one before)
-An appeal for an animal shelter... have a box or two set up in the school commonroom and ask people to bring in dog & cat supplies or old blankets which will be donated to an animal shelter.
-A Raffle
-etc etc etc etc
The best advice I have received in terms of school fundraising is to allow your-self plenty of time to organise the event and if possible, rope a couple of your friends in to help you out. Also, make sure you plaster the school with advertising so EVERYONE knows whats going on