am struggling to see why you need to be within 1m at secondary schools in 'most' cases.
The issue with secondary schools is, as tbh it also is in primary, quite simply one of space.
A standard secondary school classroom, with 1m social distancing between the adults and near-adults it contains, will accommodate 12-15 people at maximum, compared with the 25-35 it accommodates normally.
A standard secondary school corridor, with pupils waiting to enter classrooms and those moving along it, has between 0 and 0.5 m between people at best.
A standard secondary school canteen, serving pupils and requiring them to be 1m apart and allow for cleaning of surfaces, would have to serve lunch all day.
I won't bother to go into toilets and handwashing. The issues are obvious.
1m might be possible, but it's not possible to combine 1m with normal numbers - and finding enough spaces to double the number of classrooms, and double the number of teachers to accommodate all pupils is not feasible.