Hi, we live in Cashmere in Christchurch. Our children went (2 still go to) Cashmere High which they all think is just as good as the school they went in the UK which was one of the top 100 state schools in Britain - Lady Manners in Bakewell, Derbyshire. Burnside is the largest school in the southern hemisphere and some children find it a bit daunting.
Schooling here is not pressured. The facilities are mind boggling especially for extra curricular stuff and there is little impediment for children who want to work hard or diligently. But if they don't, they will not be pushed by the system. They are more interested in producing a 'whole person' here rather than getting off on academic targets and results.
Private schools are not as far apart from the state system as they are in the UK and I personally see little point in going to one. Fendalton is a very expensive suburb and suffers from all the disadvantages of the flat - no views, smog in winter and frosts. On the hills there are views, no smog and far fewer frosty mornings (not that there are that many anyway) Sumner is now hideously expensive - anywhere with a sea view is now - and a fair travel into town. The rush hour only lasts about twenty minutes though. Chch is a software hotspot and they are pushing to develop it into a centre of excellence for IT development.
Sorry, i can't write more now but it is late here and I only just discovered the forum. I will help if I can. You have to live in Zone, by the way, for your children to go to a particular school. They are very strict about it. Any school will fax you a zone map if you email them. They all have websites.