I went to Tiffin (from a private prep school) whilst my closest friends from prep school went to Putney High (private), St Mary's Ascot (private boarding) and St Paul's Girls (private). Some of my friends now teach at Tiffin.
The experiences I had at Tiffin were essentially the same as the ones they had, except I got better grades. We all got rejected from Oxbridge!
Tiffin was AMAZING for drama - I went on to perform professionally as did lots of our alumni. Loads of school productions plus opportunities to perform professionally, also with the boys' school. Also there was a trip at least every month (highly subsidised) to the theatre - both West End and more experimental off West End stuff.
Residential trips - there was loads in Y7 (bonding ones) and these continued into Year 8 and 9 (went abroad to France etc) plus ski trip, sports tours etc
Sports - incredible - competing in nationals for hockey and netball and in PE we got to do yoga, self defence, loads of brilliant sports. Plus there is a canoeing and watersports activity centre across the road so summer term you would do PE there. Also you could do Duke of Edinburgh either on foot or in canoes and if you did canoes you went to do the expedition in Malta.
Music - orchestras and choirs galore, like Jazz, Chamber, full orchestra, musical theatre - multiple musical activities every day, plus involvement in the Borough-wide orchestra which then toured internationally. Lots of girls went on to Oxbridge as choral scholars.
MFL - excellent. I did French and Spanish A Level, of course there were native speakers teaching!!!! And in Feb half term we went to language school in a French or Spanish town which was fab.
Art/design tech - there is a kiln for clay, a whole metalworking department where we made jewellery, textiles, excellent fine art dept.
Science - yes there's practical lab work (sorry I was more a humanities and arts person but we definitely did plenty of practicals in Y7 to 11).
My grades were better than my friends who went private (straight A*s) and I was not someone you'd have predicted that for - I actually only got into Tiffin on waiting list as didn't score highly enough on 11+ initially. Also, I'm the only one of us who is still actually friends with the friends I made at secondary school - the other girls who went to private school seem not to have kept in touch so much. Tiffin is a really bonding experience and a lot of effort goes in via the house system to ensure close friendships.
The hardest thing for me was the commute and that can be so daunting for young girls. If your daughter wants to go to Tiffin and the commute is better then I really really encourage her to do so. I'm really proud I went there and couldn't have had a better time. Can't believe it was free.