If you want local perspectives, it would be worth posting on MN Merton & Wimbledon too.
Traditionally the secondary schools in Merton seem to be rather undervalued by parents, despite the fact that all hold 'Good' or 'Outstanding' OFSTED ratings. In part this is to do with having nearby Sutton/Kingston super-selective grammars on our doorstep and one of the most highly rated comprehensives in London, Graveney, just down the road in Tooting. I have it on good authority that this year 60% of parents with Year 6 DC put an out-of-borough secondary school as their first choice.
teddygirlonce rightly mentioned that the two most local (and indeed only) boys secondary schools in Merton are both in SW19: Rutlish (Merton Park) and Wimbledon College (Wimbledon/Wimbledon Village). The latter is a faith (Catholic) school.
The primary schools in the vicinity of both secondaries are all well-regarded and highly sought after: Pelham, Merton Park Primary School, Poplar and Wimbledon Chase all close-ish to Rutlish; with Bishop Gilpin CofE, Dundonald and St Mary's RC Primary School closer to Wimbledon College.
Note that Wimbledon traditionally has had 'black holes' for primary schools with some families' children not being eligible for any of the local schools. Instead offered places much further afield (in Mitcham and Morden). This phenomenon has to some extent been addressed by local schools moving over to two if not three form entry in recent years.
However, it is worth doing lots of checking with [email protected] before you determine where you want to live and which schools you are interested in.
Lots of families will move in/out of borough during the school summer holidays (only three months away), so there will movement on waiting lists/vacancies at local schools ahead of the new academic year.
Good luck.
Kate