Shazjack I?d suggest trying to find some h/e dads for D/h to talk to in terms of getting him educated about what home ed really is all about, in case you do need to at some point. He is the one being ridiculous, for not facing what he?s afraid of logically and finding out about it before dismissing it.
For many men, their son not coping with school equates with failure, and the idea of home ed equates with their son ending up ?weird?. It?s a very common view were I am, and is fear of the unknown.
We had the LEA threatening court too after school kept sending him home because he?d been battered in class, or marking him not there because he was turning up late having been beaten up on his way in. They offered an escort to get him in, but wouldn?t do anything about those attacking him. In the end they sent him home as ?no longer fit to attend? and told me to get a sick certificate from the Dr to that effect, then a week later demanded I write a letter saying I?d taken him out.
Being uninterested in why a child is having problems, and threatening parents rather than trying to resolve the child's difficulties, is a very poor school.
It is just attempted bullying, but you may want to quietly drop it to d/h that if it came to such action, (which would take a total lack of co-operation between school and yourselves to really happen) he?d get taken to court too.
H/e here (older teen) includes re building clutches, engines and gearboxes, welding, soldering and sailing, as part of physics, maths, sport and life skills. Possibly not the image of h/e your d/h has?