We have 3 full time SRO's that go between the schools throughout the day. They mainly teach DARE, but provide police presence as well.
I dont think I'd be well suited to "guard duty" at the schools.
Going back and forth to the different schools and teaching a class or two throughout the day is one thing, standing guard at the gates or in the office might lead me to swallow my tongue.
I would definitely not volunteer for that detail.