My DD is in Yr 9 at St Josephs. She loves it - perhaps not as academic as Abbey, but excellent all round education - high demands /expectations in all areas, and no chance of her "slipping through the gaps" due to small class sizes. All children are encouraged to become involved in all school activities, and this gives most of them an incredible pride in their school. DD is desperate to stay at the College for A levels, in fact is totally against going anywhere else. I think this speaks for itself
St Jo's being Catholic can put some parents off, we have had no problem with this (obviously).
Friend teaches at Abbey - her DD is at St Jo's, as SJ suits her better. Look around both schools.