School Not Recognizing Father As Per Mother’s Wishes But They Have No Custody Agreement

My husband and his ex have never had a custody agreement. When he tried to reach out to daughters counselor regarding mental health concerns he has about his child the counselor responded saying he is not listed as a parent. Mind you, we’ve both picked her up from school on numerous occasions, and he’s called on previous occasions without issue. So tonight he called his ex and asked her to add him so he can speak to the counselor about his concerns and his ex basically said “if you want rights take me to court.” It’s all just a power play for her because she’s intentionally interfering in him trying to get mental health help for their child who is asking us to help her get counseling. She also does not believe in mental health sooo there’s that. He was trying to avoid having to take her to court because of their child’s fragile mental state he didn’t want her to be stuck in the middle. Does he have any other options?