Check out the "Lay" of the Land There.
IF the school is positioned so sound generated there would travel quickly to a lot of residential sites, wanting to be a good neighbor, outdoor speakers might have to "Go".
My Ravens Grin is in a small valley and such sounds travel very quickly and unimpeaded right to the houses on the hill.
This small village of elderly people like "Quiet" and I like to get along with everyone so I had no trouble disconnecting my October outdoor speakers here. As I face that hill half of it is grave yard so the UFOs that land there run on very quiet mode.
Then on a Sunday afternoon Harleys come to town and you can hear them from 2 miles away!?? WTF?
Inside you should be o.k.
Our county just adopted the new "noise abatement" which is pretty close to the levels that you are in for. We are a 75% outdoor event, and we are approx 2000ft from any neighboring property line. A residential property can receive no more than 55dBa after 11pm. So we turn off all of the noisemakers, and we make sure that any band/dj/performers are finished before 11. Before the noise abatement was adopted it was a nightmare... but now that there is a definite line in the sand, you can take necessary adjustments.
If you believe it to be an issue, you can purchase a decibel reader that records for around $600. Some offer a calibration certification card (which your measurements would hold up in court).
Considering that you're going to be indoors, I wouldn't worry about your noise pollution