Like Dan Pa mentioned.
The easy pickins may have been cleaned up by others already.
You need to dig up some of the iron to see what it is.
If its nails then you may just have to be a little more selective in choosing spots with a little less accumilation of nails.
If you find a lot of metal junk , hardware ( hinges, glass, door parts , etc)around the building it probably means this is not the very orginal but built after original have been torn down or partially repaired. If its metal pieces from metal roofing then you are in for almost an impossible hunting situation.
I had similar problems with metal roofing pieces and gave up . Just plain to much digging for nothing.
All those old buildings had outhouses some where .Also kids played near the building during recess.But not necessarily up against the building. Scanning the grounds out away from the building may be more productive then up against the building. Scanning the grounds about may become a sort of detective work for you. I have made a game of it so to speak when I was just plain looking for someplace to detect and came up with some suprising info at times. I had found where an actual battle during revolutionary times must have taken place other then where the historical markers and some buildings where located, stating this is where , etc. It actually was those markers and building were more for tourist attractions and convience of historians not really doing a fine tune location. Which made it nice for me as no detecting on the historical site. I did not need to. I believe my historical site a lot more accurate. Especially when I did my own research a little later.
But not to do gloom , but how many people attended this school, just how many possible coin drops would you expect to be there , did they have any picnic or other outings at that place, and how many people attended.
I am mentioning this not to make a research of it but to just imagine the possiblity of finds that may be there. Of course that single valuable find but thats like the lottery winner. What time period is involved that kids had coins in their pockets to loose, school lunches where brown bagged not bought.
If there was an old country store near by then penny candy type of pocket change maybe.
An old high school ,or church that type of place increases your odds tremendously compared the one room school. If the places to detect have just a small amount of people then they should be almost virgin places to detect and not covered over by massive amounts of junk, as the time and work to do searches becomes pretty valuable in itself . As the time spent in better places would be much more enjoyable.
HH
Dan R.
"> Good Luck and HH!