I stand corrected. They used to have a very strong Latin and Classics department. I think it must disappeared with the removal of the grammar stream. How time flies!!!
Boys in the last grammar stream at Glyn (it was abolished around 2010 for 2011) have not studied Latin. It must have been abolished some time ago.
Boys of the same age have not studied it at Sutton Grammar and it is only compulsory in Year 7 and 8 at Wilsons because they start GCSE options in Year 9 where Latin is optional but French or German is compulsory.
It is possible to live close to Sutton Grammar but still have an easy journey to Tiffins so, if Latin is going to be a deciding factor then it may be that you've already been allocated the best school for your son.