I used to work part time and term time only. The job was not related to schools.
I had originally been working for the organisation 3 days a week (0.6) and asked to make the change.
I couldn’t afford to take a reduction in pay so increased my weekly hours to take account of the fact that I would be working fewer weeks.
I remember starting from the point of view of wanting 13 weeks off so made a proposal to HR that I wasn’t contracted to work for those weeks. That turned out not to be sensible - partly because I would be entitled to additional leave based on the hours I was working, which I didn’t want, and partly because I would have had virtually no bank holiday entitlement (because all but one of the bank holidays fell in times I wouldn’t have been contracted to work).
I member playing round with figures a bit and we ended up in a position where I wasn’t contracted to work for 6 weeks in the summer. I used my “normal” holiday entitlement and bank holidays to cover the other school holidays. Every year I had to tell HR what dates my non-working weeks would be, because obviously they were different every time.
I had a choice of whether to be paid for the hours I worked each month or to have my annual salary paid in 12 equal instalments. I chose the latter.
It worked well when I first changed, because there was no one else in my team with school aged children so they didn’t want to take holiday in the school summer holidays.
I was always lucky with being able to take my holiday in the other school holidays too, partly because people knew I worked term-time only but didn’t understand exactly how my contract worked and just assumed I wouldn’t be there.
It became less convenient when I changed role because the make up and role of the team was different and my frequent absences were less easy to manage. I ended up doing quite a bit of work when I was supposed to be off, but always from home, and I accepted that as a quid pro quo for retaining the term-time only arrangement.
In summary, it was a bit complicated to set up, but worked really well and it made my life much easier.