Hello, Sorry about this problem. If the situation comes in way of family peace and school education, please get him assessed in detail (in person) by pediatric behavior specialist and get a prescription therapy which should be tried for few weeks.
There may also be learning disabilities which may come to light. Meanwhile please devise a reward and punishment regime for him, explaining to him and stick to same, all adults acting in unison.
At times there are some brain circuit disorders due to chemical transmitter alterations. Drugs may help here.