Here is a selection of articles that might help inform your secondary school choice:
http://dro.dur.ac.uk/20400/1/20400.pdf?DDD34+DDD29+hsmz78+d700tmt
https://www.oecd.org/pisa/pisaproducts/pisainfocus/48482894.pdf
https://www.theguardian.com/education/2012/jul/30/best-educatioon-state-school-not-private
Grammar Schools v Comprehensives
The May government’s case for more grammars: https://www.theguardian.com/education/2016/sep/10/grammar-schools-will-cut-private-school-monopoly-of-professions
The case against more grammars: https://www.theguardian.com/commentisfree/2016/sep/10/observer-view-on-grammar-schools?CMP=Share_iOSApp_Other
Sir Michael Wilshaw, the outgoing head of OFSTED, on school improvement in London: https://www.gov.uk/government/speeches/sir-michael-wilshaws-speech-at-the-london-councils-education-summit
More research from the Local Schools Network, an excellent “fact-checker” website set up by London education campaigners: http://www.localschoolsnetwork.org.uk/2015/03/eleven-grammar-school-myths-and-the-actual-facts
Adolescent Mental Wellbeing
Co-ed v Single Sex Schools and Achievement
Some opinion pieces, mostly from within the independent sector: https://www.theguardian.com/women-in-leadership/2013/oct/30/co-educational-schools-bad-for-girls