I attended the school until 1999.
MHS is a fantastic school with some excellent achievements and fantastic staff, management team and governers.
Marple/Bridge/Romiley/Offerton is a strange area in that it has a mix from each of the far ends of the social spectrum or demographic classification. From what I've seen/personal experience, this vast mix brings with it some serious social problems - from either ends of the scale!
These appear to be dealt with well by the school. Knowing a number of people who attend, and a govenor at the school, if the child wants to do well and succeed, they will - support must come from home too I guess!
The big question I'd ask is if it intends to become an academy? (does it? - I haven't heard any more recently)