First off, the First Amendment ot the U.S. Constitution prohibits public schools from enforcing rules that impose a substantial burden on a student's exercise of his or her religion, unless the school can show a very good reason. So, for example, a school must allow a student to make up a test that she missed because of her absence during a religious holiday. The school's interest in having a student take a test on a particular day is not important enough to ignore the student's interest in observing her religion. A student, however, must show that following the rule would cause her to violate her religious beliefs. In other words, a religious belief cannot be used just as an excuse for avoiding a rule that the student simply dislikes.

In light of the concerns about school safety, a court probably would look very skeptically upon a student's claim that the First Amendment gives him the right to wear a knife as a religious symbol. But it is still possible that a court would agree with the student if certain conditions were met.

First, the student would be required to prove that he sincerely practices a religion that requires its believers to carry a knife. Second, the court would balance the student's interest in practicing his religion against the school's interest in safety. In balancing the interests of student and school, the court should consider whether the school could accommodate the student and avoid serious safety risks.