I am a lawyer in CT, not IL, however, I practice criminal law.  I am not sure how old your son is, however, i am sure that the school is going to get involve and take this very seriously.  As for an arrest, I am not sure if they will take it to that level.  Rather, the school may expell your son where he will have to go to another school.  However, i am sure that there are ways to get all the parents in the room and have them understand that your son meant no harm and to chalk it up as a bad day to avoid having either kids be embarrassed.  Nevertheless, the school is going to be afraid that the girl's mom could sue them if this happens again.  Therefore, I would expect the schoo to take the most serious action here not the police.  I would check with a lawyer that deals with juviniles to determine the age that they prosecute minors.  You did not tell me your son's age so i am not able to give you a definitive anwers.  You should arm yourself with a lawyer, especially dealing with the school to avoid an expulsion.