The Earthsea trilogy by Ursula Le Guin is another one (there are also books beyond the first three now, but they're more targeted at older readers).
IIRC, the name for rabbit was kebbo or something like that, so if you called out the true name for rabbit, any and all rabbits would be affected. This would then hold for petals as well?
Also, the secret to exiting the school (getting past the guardian) was pretty cool.