This is a large topic.  Some of the keys include what parents can do and what teachers can do.

Besides psychological treatment, let's discuss some things parents can do.  I remind us of the behavioral rehearsal, specifically the goodbye ritual.  Another reminder of healthy attachment with two moments of warmth per day.   A reminder of the importance of speaking good into our children / and calling good out of them.  

Some things for teachers to consider, besides parents open to their words and influence, thus maintaining open communication with parents to give them that chance, and open communication with the counselor, include scaling anxiety and safe zones - while sensitive of potential for avoidance.