What sort of thing do you want to know?
Your DS will be in one of four houses (even with the +15 intake this year, they are keeping the four Blue, Brown, Green and Red houses)
As well as sharing the same house as the rest of the boys in his form and older boys up the school, they will participate in lots of house events: sport, drama, music, poetry, science etc which are great for team building.
As well as one day in school in the summer term to meet his new form teacher and classmates, and a separate social evening at Northey sports ground for boys+parents, the school also runs 4 summer activity days for new Year 7s in August: they are well worth going along - they are based around football, cricket, rugby and basketball but no level of skill is expected, they are just fun days to meet up with other boys.
It is a great school and provides lots of opportunities for the boys to get to know each other and settle.
The PTA will also sort out a contact list for your son's form so you can hook up with other people travelling from your area if you don't already know anyone. Because Sutton has good transport links, boys come from all over on buses and trains.
I think it is around May that you get a big bundle of paperwork from the school with more information and loads of forms to fill in.
Good luck to your DS, I'm sure he will have a lovely time at SGS.