This to me sounds like the district needs to be providing and paying for an adult one on one assistant for this child. I would document, take notes of all incidents of perceived aggressive behavior (do not put any subjective descriptions simply say: 9 a.m. Jane Doe took hand and hit John Doe on arm, 10 a.m. Jane Doe with both hands pushed John Doe and John Doe fell to ground, it would also be good to have a narrative, but only say what happened, nothing extra,) and call an IFSP/IEP and request additional support from the district or what we called in California the regional center.
This is not just for the benefit of the other students, but the student. The student needs to learn appropriate social interaction skills in order to fully benefit from being in a classroom with his/her peers, if students are afraid of the student owing to perceived by other students as aggressive behaviors, the student is losing out on valuable socializing opportunities. The student needs support as soon as possible.