Goldpony, glad you found the map useful. I created it from the information provided in the County Council's schools information booklet. The council web site has their own map but there are a few discrepancies between it and the booklet: e.g. the map shows Orchard Street as being in St Matthew's catchment whereas the booklet lists it as being in Park Street catchment. I would take the booklet as authoritative. My map is, as far as I am aware, completely accurate.
The Council's guide to school admissions is also very helpful, although the admission criteria for each city school are also set out in the schools information booklet.
Regarding schools on and around Mill Road, the general thinking is that the town side of the railway line is fine, the far side more challenging. St Paul's is a very good school by all accounts. St Matthew's had a mediocre Ofsted report a few years ago but that was at a time when it was going through staff transition and had an acting headteacher. The latest report is much more positive, results have improved significantly and the school appears to be on an upward curve.
Over the bridge, the teaching at St Philip's gets a lot of praise but the school's results are held back by a higher number of children with learning difficulties and those without English as a first language, being situated in the Mill Road melting pot. Ridgefield is considered to be the weakest of the Mill Road area schools.
There's been quite a bit of talk about Park Street. It is a good school but, being far and away the smallest school in the city with a correspondingly tiny catchment area, it's also difficult to get into. The catchment is basically the town centre (i.e. shops), the ancient colleges (i.e. students) and two tiny residential areas: on the streets between Bridge St and Jesus Green, where many of the houses are college-owned student accommodation, and on Castle Hill, between Castle Street and Madingley Road.
From outside of catchment, places are awarded based on straight-line distance from the school. Practically, that means if you don't live in the De Freville area or the 'wedge' between Victoria Road and Chesterton Road, I should think you're unlikely to get a place. Of course, a mid-year opening might be the best opportunity, but pulling your kids out of school mid-year is a big decision, unless you're really unhappy with where they are.
I think Marmee has it right though when she says that there are very few bad schools in Cambridge. It's an affluent, cultured city and consequently many if not most schools are between good and excellent. Most likely, wherever your kids go they'll be fine.
Atzan