As someone who has actually done this, I can tell you if you’re thinking about it, then do it!
My DD loved the Sats, found them easy and then was bored as the next few months were going to be spent catching others up who were behind!
I deregistered her, at her request, and home educated her. She loved every minute, being able to spend longer studying topics and subjects she enjoyed, completing art work with no buzzer telling her to stop, finding subjects such as marine biology and criminology she could study instead of others she found a lot less interesting.
she went back in year 7, but found it so boring, back in the 4 walls, being told what subjects she should study, have length of trousers checked, being told to wear a blazer, by someone in a blouse, when too warm… those few months out, she had learnt to think more for herself, make more informed choices, instead of just doing as told, aimlessly…
6 months in, she asked to deregister again and never looked back! She kept in contact with her schooled friends for years, meeting up, hanging out, had new home educated friends, socialised with all ages not just her peer group, as went to skating and gym clubs so had something in common with the attendees of every age….
10 years down the line, she is a well rounded, successful, confident member of society, who is so thankful she was listened to. Do it, you won’t regret it, and these days there’s soooo much available in terms of online tuition, and 10’s of 100’000s more in the same fortunate position.