DS has always had my surname, and had his dad's surname as an additional middle name (which is what I did too when I was married). Divorced 2 years now. DS also has another middle name that comes first, so his full name has two surnames at the end.
Ex-H is angry that I'm not using his surname for primary school. He thinks we should be using both as a double barrelled surname. FWIW if Ex-H was more involved in big decisions i wouldn't mind this so much but when DS started school last month and it was exes first time doing the school run, he actually had to ask me what school he goes to. I tried to involve him in all of this from the start but he just said "you sort it, you know what you're doing".
DS came back from his dads yesterday asking me why I wasn't putting his "big name" on his school book bag etc and I know this has come from his dad and has confused him. I've reassured him his name hasn't changed and he still has all his names but that we just use our first and last names. He was happy with this. And he likes having his surname- the same as his grandparents and cousins (he doesn't have a close relationship with his dads family).
Doesn't help that he is one of four children in his class with his first name, and we have a short, easy to spell surname whilst his dad's surname is long and complicated.
AIBU? Should I just start using double barrelled? He has regular contact with his dad but his dad has zero engagement with school, paediatricians, social worker, therapists etc (DS is undergoing assessments and is entitled to a specialist social worker, he doesn't have one due to parenting concerns or vulnerability at all).