I cannot see too much to be had inside the school, unless it is one of the really old dirt floor types (Most of these have deteriorated to the point of not standing anymore)??? if you do get inside, I think it would be more productive to hunt with your eyes and brain than with a detector...if there are covered registers (radiators), check those out...the younger kiddies love to stuff items into strange places. Outside, I would suggest hunting any visible tot lots, the grassy expanses, and under any good sized trees...Kids love to climb trees. In a large area, take it in sections...look at the layout, then picture a grid in your mind...I usually hunt a 100 by 20 yard section a day, and pound it hard, going over it like 3 times...The next day, I move over to the next 100x20 area...You would be surprised at what I missed on a first pass over an area...It all depends on how your coil crosses your target I guess...
HH,
BH-LandStar