Subject availability to match what your nephew wants to do is the key here: while schools will list a wide range of subjects, the timetable may not actually cater for the options required: this even applies in the full price fee paying schools.
The idea is to have the widest choice of subjects so as no higher level options are excluded because of poor availability in the school of the necessary subjects.
Likewise, education is not just about the school, its about the child and the interest in education in the home, as well as the particular teachers that the child interacts with.