I have audited 3 work canteens which must follow similar lines to school canteens.
To start off with; all three had supposedly implemented HACCP but no-one on site had been involved in its writing; all were written by consultants to the contractor. This meant that there was no buy in and little understanding at all sites. They all knew they had a HACCP plan but none of them knew what a CCP was.
It's simple to put in place a HACCP plan in a canteen but you need to think about processes not individual dishes (as far as you can) and you need to train the staff so they at least know what a CCP is and what to do if it goes wrong and also what processes have been considered (so they don't do something different.)
Remember the first page of your HACCP plan will be "who is our consumer?" or something along those lines. A school canteen produces food for children and so the risk of illness is higher and the PR consequences are huge.
Processes I would look at include:
defrosting (consider some ingredients e.g. cakes may be defrosted then eaten cold)
cooking
cooling
reheating
hot holding
chill holding
washing (e.g. veg)
opening packaging
storage of ingredients (chilled, ambient, frozen, including labelling and what to do with part opened ingredients)
Cutting
There are probably more but you need to look at your process. Don't forget in all this that HACCP can be a waste of time if prerequisites are not in place. The amount of times I have seen store rooms held open with tins or packets on the floor or inadequate hand washing is unbelievable. As there is no high risk and low risk, it's important that colour coding of utensils is in place and used.
Certain items will be necessary to treat as special cases; for example, in a canteen environment, I would never allow rice to be reheated (even though if done properly it can be done safely) because the risks of someone not understanding is high.
Most of all, I'd get someone compitent to audit. In all three canteens I visited, I found something wrong with temperature control. In one, the sandwiches were at 10 degrees celcius. The response from the manager was "I've told engineering". After I threw out two bin bags worth of stock and visited daily for the next month, I think the food safety message started to sink in.
