On the criminal law end they can not without a warrant or court order. But in school regulations are not my area. There you need to speak to a education law attorney. My guess is they can ask and suspend.
This is an area of law that is well defined. The test must be "reasonable" and comply with both the New Jersey and United States Constitutions. The method of testing, notice given and other facts specific to your case will help determine whether you can be compelled to take a drug test. You should speak with a criminal and/or education attorney asap.