I was in a similar position with my DS - he's done a lot of professional theatre including WE and wanted a school with really good performing arts opportunities. We are also North London, and considered the following:
- City of London Boys - 11+ and 13 entry, very good academics, appears to have good drama, school has own theatre, great music, has experience of pupils working professionally, doesn't offer drama scholarships.
Forest School - 11+ and (small) 13+ entry, co-ed, less strong academically, supposed to have good drama, has its own performance space, looked at me like I had two heads when I asked about whether they were supportive of pupils performing professionally.
Emanuel School - south of the river near Clapham Junction but commutable, 11+ and (small) 13+ entry, co-ed, reasonable academics, looks to have good drama and offers drama scholarsips, has quite a few pupils who perform professionally and seems supportive of this (e.g. online systems for catching up on missed work).
Whigift School - also south of the river in Croydon, 11+ and 13+ entry, boys only, good academics and drama, offers drama scholarships, has pupils who perform professionally and appears supportive of this, very sporty school generally.