I would just enrol him then. You did try. It's not like you didn't even consult with him about it.
As far as new partner, thay may just be the case. But personal story - I was the second wife to my ex (he has a daughter from first marriage). When my ex initiated mediation to get more time with daughter, the mother assumed I too was the driving force. Nothing could be further from the truth. I was young and selfishly, didn't want the daughter around anymore than she already was! Ex's daughter has lots of issues and I couldn't deal with her.
Anyway, just wanted to share as she was dead set convinced it was me who encouraged ex to pursue consent orders etc.
I find with the messiness of blended/ex families lots of assumptions can be made. Not saying it's not true just giving my experience.
The driving force unfortunately for his father is always that someone is watching, for example when he was in Australia he was terrible at doing his visits, dropping him back after 3 hours, canceling etc the second he went back to his home country and was living with his parents there was no missing Skype, planning trips back etc once he left his parents the Skype were whenever he could be bothered and barely a word about coming out for visits, now he has been dating this person (she also has two kids) its ramped up, like when he lived with his parents.
I dont think it's so much her wanting access to our son, but it's her asking questions, and because he has hardly been involved he cant answer them.
we had a huge fight when our son was two and he told me I owed him an apology for not having an abortion, I responded "you never had to stick around, I gave you an out and told you I could do it all by myself" his response was "yeah like that's an option, what would people think of me" not i couldn't abandon my son, how could i not be in his life, but what would everyone think of me if i had done that.
He is a narcissist, and a sociopath, he actually mimics people to create fake bonds and friendship, I notice after we were not on good terms, everytime he had a new important person in his life he switched his drink choice to theirs, with me he drank lattes, a business partner so then it was mochas, the new girlfriend came along it was chai tea etc etc he mimics interests, food choices, like seriously he just becomes a version of that person and he gets away with murder.
Because I stand up to him he pulls these stunts, it's all about tormenting me and really he wants to win and in this scenario he wins no matter what, I send him to private school I have confirmed his narrative of me to his girlfriend, see how I disregard him and block him from being in his sons life, I dont send him to private school, he loves that he stomped on my plans for our son and hurt me.
I'm definitely going to send our son to my school choice, I dont care if he tells the world I'm a giant meanie, i have countless pages of me offering time, rescheduling my life so he can see him, bending over backwards for them to have a relationship, I dont care what anybody else thinks of me.