My mum is a retired teacher.
My situation was similar(ish). DS was v good (exceptional) at maths and bored as hell. Average in other subjects.
Advice from mum was at this age, children’s progress isn’t linear. That she taught many a “child genius” that a year down the line was on par with peers who had caught up.
In short, trying to skip a year is pretty premature at this age. There are also consequences down the line.
I was at school with a child who’d been bumped up a year by her parents. She was clever and did well academically but emotionally I know she found it hard.
She felt “marked” as being clever and massive pressure to live up to this. She was also behind key milestones such as learning to drive, being able to go to the pub and drink.
Those may sound small things (and to be clear she was a friend and liked within our little gang and nobody teased her) but it did bother her.
Far better to speak to the school and see what can be done to stretch your child in the year group.
School was amazing with DS in giving him more challenging maths work along with another pupil who was in the same zone.
Wasn’t a big deal. They all got the same work in the class with a breezy “if you finish x you can come and get y to solve”.