lol @ sarah's wildlife collection
We were always luck enough to have access to the primary school's pets, they had gerbils,FS class had guinea pigs and chuckling at the memory ~ our lovely Caretaker almost quit when one of the teachers decided to bring his pet rat in
lol
I think they are a huge benefit to the children (and staff ) although you also have to ensure they are brought into the group responsibly with all the 'homing/illness/risk considerations taken into account !!