a lot depends on the new head, staff and the cohort tbh.
I think that is so true.
When my DD1 was about to enter 6th grade (in the US) in a parish K-8th grade school the local junior highs converted to middle schools, taking in 6th to 8th graders, so three years for the middle school cycle. We were tempted to take DD out of the parish school and go public because the facilities were amazing - fab science labs, gyms, art facilities, etc. We decided to keep her in the parish k-8 school because her classmates were a great bunch of people, the k-8 offered great leadership opportunities to the kids in years 6-8, and it was a lot smaller than the big middle schools. Plus she was doing very well academically and we had no worries about her ability or motivation. I think she would have thrived in either place tbh, but we knew what we were dealing with in the parish school whereas the new middle school concept was an unknown.
I seriously considered sending DD4 to the middle school many years later and I still sort of wish I had bitten the bullet and done it. Her female classmates were a cliquey bunch and she was struggling much more in maths than the teachers realised or bothered to assess. She would have got the intervention she needed in the middle school.
What I heard from people I knew who went to the middle school in its first year was that there were teething pains - the administration had not anticipated the social or academic needs of a sizeable cohort of troubled 6th graders who were funneled through from two of the public elementary schools that had had high admin turnover in the previous years (six principals in 8 years for one particular elementary school) with the resultant lack of continuity and low teacher morale not taken adequately into account. Students who had experienced quite a it of upheaval in their previous educational environment were a bit more disengaged than anticipated, and had suffered academically too.
Additionally, students from the piss poor major city school system next door were increasingly moving to the suburb as their parents wanted to get them into better schools, but they were much further behind their peers on arrival than the middle schools were equipped to handle.
Individual circumstances, I know...
But imo the caliber of the administration team is very important.