[ZenGum]

I'm reading a US teacher training manual right now (long story) and I think the teacher cannot share info with you without very clear written permission from the parents. The teacher has to cover themself legally.

I suggest you contact the teacher and find out exactly what kind of permission is needed, so you can get it. Then you can talk.

Also, the teacher might be a bit defensive - sad child is a reflection of an unwelcoming classroom, which doesn't look good for the teacher. The teacher might try to direct attention on the child's home life. From what is written here, the teacher might have a point.