I've no idea! It's very irritating as we have the same thing here. I live on the border of 3 counties and am a cm'er. So this week I will have extra children (just not today) as well as my normal term-time children, and then next week nobody apart from my own dd! Which is actually working out really nicely and we can have a lot of fun together, but it means that where she'd normally have people to play with she hasn't, and I have to juggle big kids as well as my normal smalls with our regular activities.
October half term, mine & daughter had different weeks. Here comes February half term & the same is happening again . Anyone know if there is some grand plan in the country as to why neighbouring boroughs are at odds? If there is, I may well have to consider changing schools as it is such a pain not getting that week with DD!