False accusation of a minor with disabilities for sexual harrasment from a teacher .

My son and his cousin were accused of sexaul harassing a language teacher off school grounds on sovergn Land. she had promised them cupcakes on monday.. so friday after school on the seneca terratory in a conveint store the boys ran into this teacher ( who is not on the schools payroll) and the one boy said hey cupcake where is my cupcake .. the other said when are u taking me to a movie.. she said what ever and walk away.. following monday she was in class and over heard the boys say hey u remember what happened this weekend .... and she rudly butted into the conversation and said I remember what happened and the boys smiled and asked her did you bring our cupcakes and Half and half.. she replied I was to lazy to make them. later that day the boys in 8th period were pulled out of class and were talk to by the princapal of the school about the matter they said yes to sexually harassing the teacher.. the princpal was not aware of the statement the boys said to the teacher.. so he asumed that it was sexaul and vulgar.. so the boys recieved 4 days ISS... and kick off the basketball team. does my son have any rights... he has never said anything disrespectful to her in school and she admitts to this.. and he is being punished for sexual harrassment and the teachers and bus drivers and students have judge him. when he only said are u taking me to the movies is that sexaul harrassment.. it never happened on school property but the fact it was brought up in class by the teacher that my son is getting the blame for it when she brought it up he just smiled and giggled and said were our cupcakes and half and half..she has no proof her word agaist the boys the kids in the class state that he never said anything to her in class that was sexual .. she has no documention of any sort.. I told the princpal if she felt threated she should of called the police of the tribes marshels.. or called me as parent.. I feel that the punishment is to harsh for the crime.. innacent flirting from 13 and 14 teen year old. both boys said sorry and didnt feel that they sexauly harrassed her. now there names are look down apon because know one has the specifics .. they just hear sexual harassment. Does my son have any rights..?