Do we have to be warned that we are trespassing before we are charged?

The school is not required to give you a warning before having you arrested for trespassing. The presumption is that you may not be on school property. Minnesota law makes is a crime to be on school property, unless you are a student, parent of a student, guardian of a student, a school employee, have permission or an invitation to be on the school property, or have reported your presence to the required officials. The relevant statute is Minnesota Statute 609.605, Subdivision 4. Trespasses on school property. (a) It is a misdemeanor for a person to enter or be found in a public or nonpublic elementary, middle, or secondary school building unless the person: (1) is an enrolled student in, a parent or guardian of an enrolled student in, or an employee of the school or school district; (2) has permission or an invitation from a school official to be in the building; (3) is attending a school event, class, or meeting to which the person, the public, or a student's family is invited; or (4) has reported the person's presence in the school building in the manner required for visitors to the school. A misdemeanor is punishable by up to 90 days in jail and a $1,000.00 fine. It is a gross misdemeanor if three or more people violate the statute. A gross misdemeanor is punishable by up to 365 days in jail and a $3,000.00 fine. (c) It is a gross misdemeanor for a group of three or more persons to enter or be found in a public or nonpublic elementary, middle, or secondary school building unless one of the persons: (1) is an enrolled student in, a parent or guardian of an enrolled student in, or an employee of the school or school district; (2) has permission or an invitation from a school official to be in the building; (3) is attending a school event, class, or meeting to which the person, the public, or a student's family is invited; or (4) has reported the person's presence in the school building in the manner required for visitors to the school.