I detect old schools, especially the old one room 1800's schools. I have hit at least 3 of them recently. The first 2 were a bust, the one I'm currently hunting, has been my best site ever! As far as schools that are still active, I might try on a weekend, or during summer break.
Some of the finds from the 1879 school, over the last 2 weeks:
1848 Large Cent
1853, 1886 Seated Dimes
1896 Barber Quarter
2 V Nickels
2 Buffalo Nickels
1 no date Shield Nickel
about 20 Wheat Penny's
1915 Canadian Large Cent in same hole with old pcket knife
1 really rough Indian Head Penny
4-1940's Mercs.
1 decorative metal button.
I'll post pics on here when I am further along with hunting this spot.
Some other odds and ends too, but definetly recommend trying them!