lol at Spinkle!
I'm a teacher, I teach primary 3 days a week. If you LOVE teaching it is a great job, but most teachers find it pretty stressful. I currently put in 10 hour days at school, plus another 15-20 in the evenings and at the weekends.
Teaching is not family friendly - apart from having school holidays with your children, which is a massive advantage, of course. Having said that, I work in the holidays - planning, putting up displays, organising resources, etc. and when DS starts school (currently at nursery, which is open in the holidays) I don't know what I will do with him!
I will also not be able to take him to school on drop him off three days a week, or so Sports Days, etc. If I worked f/t I would literally never see his school, let alone his teacher.
Probably much depends on the school you teaching in (mine is awful) but even if you think you've found the perfect set up, things can change very quickly - new heads, school going in to special measures, etc.
Sorry to be such a downer - I really wish I had listened to those older teachers who told me not to do when I was training!