@SonicStars am I understanding correctly that your DS is at the moment chronologically year 5 (were he in school now, in his age-appropriate cohort) and you are considering whether he should wait until 2025 entry into year 7, with the age-appropriate cohort, or can you start him in year 7 in 2024, when he would be year 6 age-wise?
If so, you need to have a conversation now with your local authority - and possibly individual schools - about out of normal year group admission and any supporting evidence required , because the deadline for on-time applications for state secondary school year 7 entry is October 31st.
Apologies if I've misunderstood, or if you have already taken this into account, also feel free to dismiss my contribution to the thread as irrelevant anyway, since I'm not a teacher of any description, let alone a year 2 one.
(@DelphiniumBlue , being 'accelerated' in state primary schools may have disappeared by the start of your career - which must have coincided, more or less, with the push for allowing children who would be the youngest in their 'correct' school year to be the eldest in the one below instead - but it certainly used to be a 'thing'. I was moved into the year 4 class halfway through year 3 back in the 1960s and, more recently, 2007 in fact, DS1 was moved up into a year 6 class for the second half of year 5. In both cases, though we had to repeat year 6 and enter secondary school with the correct cohort)