Middle Boy wants to go back to his old therapist.

Fine...as soon as this therapy is over we can consider it.  I would really like to go to the attachment center, but we can talk to Therapist A to see what her thoughts are on it. 

This WILL NOT happen while you are in therapy with Therapist L.  It just won't.  You already don't want to do the therapy work you are assigned.  We aren't going to waste anyone else's time.

I would love to do attachment therapy with you, but if your attitude about therapy is what it is now I will get frustrated.

Prayers for a changed attitude.