If this is simply a case of someone cheating to achieve better grades, leave it alone. You aren't the moral police. Pray for the cheaters, that God would expose them and use it to glorify Himself. Then, leave it to Him to sort out how and when.
Reporting the minor offenses of others will only make you a pariah, because nobody likes a 'snitch'. If someone is in physical danger, or there is a crime being committed, then report it, but only to the appropriate authorities.