If you take the post then your lives will totally revolve around the school. For many couples, and families, this works very well and they enjoy a great many benefits. But if you don't want that life, then it is definitely better not to start down that route. As far as the teaching goes, can you arrange to go and speak to the HT, or whoever is dealing with the recruitment, and discuss with them your concerns. Maybe don't take your partner at this stage. You might be able to take this pastoral post for now and still become a primary (effectively) teacher at the school, say in January or next September. Go and visit and talk as you would do if you were thinking of applying for a post there and be there as 'you' thinking about your career. Maybe ask on the independent board, there are people there who live at work in boarding schools with partners and families and can give you a better idea of how it is.