The answer to this question lies in reasonableness. If it can be demonstrated in court that an individual would reasonably know that the property in question was owned by a school, then the property is presumed to be a school property. So merely stating that you were unaware that the property was within a school zone is not a defense of the charge. The property must be used regularly and consistently for school purposes in order to be considered school property. If a town owns a municipal field that is occasionally used for school sporting events, that property is not considered to be school property.