About mandatory reporting. Again, I would make no assumption, at all. As mentioned above, I think transfer of students and also teachers is a common way to brush off these problems.
I was involved in a situation once where I made a visit to the counselor and called in the principal. I brought my son in as he was the one who was aware and witness. This involved another child’s parent. I was very careful in my wording, and did specifically use the description ‘abusive situation’. The counselor seemed to be receptive. The principal was annoyed and walked out within 30 seconds. As far as I could determine nothing was done, no mandated reporting to CPS. Nothing.
That is why I would report to authorities such as police and CPS.
OP, I would request that this child be separated from your daughter. There should be options, such as a special situation to deal with this boy. Unfortunately, they will not want to provide for him and might suggest moving your daughter. Insist that they address the situation with this boy,! Not shift around your daughter or other innocent students.