I deregistered my DS1 when he was 12. He tried really hard to integrate into secondary, but it was overwhelming for him and made him ill. Deregistering gave him the time to recover and gave us, as a family, time to get over the stress of his experience at school.
It's a really scary thing to do, so I sympathise with how you are feeling now. However, once you have done it, you feel such relief. We deregistered DS before the summer holidays, so he had a long time just relaxing and not even thinking about schoolwork.
Nine months later, to my astonishment, he is thinking about going back to school, although it will be a very different school to the last one. This time off has done him so much good. I have made sure he kept up with basic subjects, such as English, Maths and Science, and we have also been able to concentrate on all sorts of other things that were important to him.
I deregistered DS1 in July. I felt as if the sky would fall in, but in fact I had really lovely emails from his teachers at school, wishing us all the best.
Just follow your gut instinct, op. If you feel it's the right thing to do, just do it. Don't wait until September.