Ds is in year 9, so choosing GCSEs. He is very happy at the school and thoroughly enjoys it there.
Er, yes the teachers really do teach instead of read! Your experience of 'elite' (private?) school sounds very strange - here pupils would only be doing tuition outside school if they either couldn't keep up in class or were studying something not taught at school. Pupils are set in different bands in most subjects so they are taught according to their strengths.
Teachers vary in character, but the ones I have met at parents' evening have a very good understanding of the pupils, and are mostly patient, humorous and good-natured. They all know the boys well, and the relations between teacher and pupil tend to be respectful but quite jolly - in my experience anyway, but that could be down to ds's sense of humour and the general male atmosphere.
I haven't personally been in the classroom while teaching is going on but they seem to accomplish a lot in the lessons. The boys are certainly engaged and interested in the subjects. The school day is very full, either with lessons, activities or sport.
Most Independent schools study for IGCSEs especially in sciences and maths as they offer a more interesting curriculum.
It might help you to talk to a parent with a child from abroad boarding full-time. If you contact the registrar (Mr Gilliat) he might be able to put you in touch with someone.