Hi, do you mean the prep or seniors?, my experience is seniors.
My DD has been at St Ts for several years since yr 7. She has been well taught and challenged for her ability in year groups and, mostly, sets for a wide range of subjects. She has learned to study and not just answer exam questions with spoon fed answers. She has had space to become herself and find her own interests - along with an excellent set of GCSEs.
We chose St Ts because of its overall size, the small classes, the clubs, drama, music, the wide range of girls from both the UK and overseas, and the lovely setting - though the snow has proved a challenge once or twice.
Her teachers know her and she has not got 'lost' as we worried she might in some of the more obvious and larger Guildford/Surrey schools.
Nowhere is perfect, and I'm sure others will not have had such a positive experience, but I have not regretted our choice. The arrival of Mr Farmer at the school has had a positive effect on the school and he is very approachable about any matter.
I hope that is helpful.