Can high school students' community service be stamped with the property seal?

Of course. High school students' community service, as long as it helps the community or the property to do what it can, can be stamped with the seal of the property. The school requires community service mainly to let students get in touch with the society. Stamping is just a way to prove that you really helped the person who stamped it, so you can stamp it with the property seal.