Hi MindfulBear
Welcome to Mumsnet Merton & Wimbledon.
Would think about questions relating to particular aspects of school life (listed in no particular order):
wraparound care (breakfast club/after-school activities put on by the school/after-school paid for provision)
teaching staff (turnover, how long SMTs have been in post, TAs, ratios of newly qualified teachers to more experienced ones...)
wellbeing of the children (do they seem happy, does the school environment give off a warm, welcoming and happy vibe, safeguarding issues, how they cope with bullying, SEN provision etc...)
ethos of the school
learning (how well do the children do, added value, do they provide additional support for those who are 'Gifted & Talented', position in Merton KS1&2 League Tables - some schools are consistently in the Top 10 but some markedly fluctuate, how the children are stimulated in the arts/sports etc...)
That's just for starters. Your husband will hopefully get a feel for which school feels right for your DS - you can sometimes tell as soon as you walk in to the reception area, meet the admin staff and see how welcoming the waiting area is!
It is worth looking at the two/three most recent OFSTED reports for the schools concerned and see if they've been consistent, on a positive trajectory or the reverse. Also it helps you see what their particular strengths are (and what areas might be weaker...)
If you have an idea of where you may be living, it's also vital to ask if children from that road (or even house number - the catchment areas of some schools can be micro-managed to that level of location!) get in on distance etc.... Also a big issue with the primary schools is the 'sibling factor' which can significantly reduce the number of available places for eldest/only children entering primary school at Reception Class level. You can also contact the Admissions Team at Merton Council if need be, to clarify any related queries ([email protected]).
Good luck!