Hello from the Crossroads of America
WWW1221
Even if they gave permission, it's up to you to determine if the school is in airspace that may restrict flight due to airports, etc?
Check out the ALOFT or AIRMAP apps before you fly to check conditions in your area.
#1 FAA Approved LAANC Provider, UAS Service Supplier, UTM and Aviation Systems
play.google.com
AirMap is the the leading provider of aeronautical data & services to UAV's.
play.google.com
That'll take care of the airspace you're flying in, now it's about the property in which you launch from and that's a local thing you'll need to find out.
Property owners, parks, etc. may restrict flights from the property.
Here's a link that may help with Oregon drone laws.
A list of drone regulations and links for people flying drones in Oregon.
uavcoach.com
If you haven't done it yet, you should take the TRUST test to keep a copy with you when you fly.
Get your FAA TRUST Certificate of Completion to legally fly drones for recreational reasons in the United States.
trust.pilotinstitute.com
And of course, register the aircraft with the FAA if it's needed.
faadronezone-access.faa.gov
I fly at my local school after hours with zero activity (practice, events) and I haven't had a problem yet.
YRMV.
Good luck with your research and welcome to the Forum.