Is farting in someones face ual harment?

My son was suspended from school for farting in someone’s face. A few of the boys after gym cl were wrestling around in the locker room and my son ran over and farted in one of the boy's faces. I know this is disgusting and should be punished, but suspended for a week?? The principle wanted to have him expelled for ual harment. Is this considered ual harment?