Two vital bits of information are missing so far.
1. What was the quality of the work done by the previous photographer. Was it worse than yours, the same or better? There is no point in trying to compete on price if the previous guys price was low due to lower quality. If your quality is demonstrably better you can use that as a selling point for a higher price.
2. If this is a fee paying school then I would take a quick look at how much those fees are. Does it charge a lot, is it doing well. If so claims of poverty should be ignored.
Other points...
The photographer "moved away"*. Do you know where? Can you contact them and pick their brains on exactly what their deal was and what they thought of the client? They may tell you they made a bad mistake by bidding too low. Also the school may or may not be being totally honest with you as to the terms of the previous deal so talking to the other party may help.
Sometimes "clients" don't see the value in a product and are never going to pay what it is worth. These people aren't clients and you should walk away.
*the school may actually be a nest of vampires/werewolves and the previous tog's remains may be interred in the basement. If at any time they invite you to "stay for dinner" I would suggest making an immediate and speedy exit.


