There was a Hillbrow boys' preparatory school in Rugby in the late 19th and early 20th centuries that was attended by the famous 20th century poet Rupert Brooke (1887 - 1915) and the slightly less famous psychoanalyst and writer James Strachey (1887 - 1967). Brooke and Strachey were not only contemporaries at the school but also close friends.
Brooke's entry states that Brooke "attended Hillbrow Prep School before being educated at Rugby School." Christopher Hassell's biography of Brooke (p28-29) states that "In the summer of 1897 Rupert began his school career. Hillbrow was barely a hundred yards down the road (from his home in Hillmorton Road, Rugby), another of those solid institutional buildings erected with alternate layers of red and blue brick, without heating of any kind, and the inevitable boring draught in stone passages that smelt of dust and the leather of down-at-heel shoes. Rupert was of course a day boy and Richard's (his elder brother) first job of the day was to see him safely across the road."
The photograph below (from http://www.search.windowsonwarwickshire.org.uk/engine/resource/default.asp?resource=2178) purports to be of the interior of the school gymnasium in 1917. However the accompanying map shows the location of the school at the corner of Bawnmore Road and Bawnmore Park, which would place it over 2 miles from Brooke's home in Hillmorton Road.
Interior view of the gymnasium at Hillbrow School, Rugby. 1917
There is no evidence that Brooke's Hillbrow School in Rugby had any connection with the Hill Brow School in Eastbourne. However Peter Isaac has a recollection of Frank Matthews talking about an alumni group called the Old Hillbrovians, a Google search for which produced a link to http://www.nytimes.com/books/first/h/hale-friends.html (copied here) which quotes Chapter 1 of “Friends and Apostles - The Correspondence of Rupert Brooke and James Strachey, 1905-1914”. It includes a quote from a letter dated 7th July 1905 in which Brooke writes: “I refuse to vow anything. I know myself too well. My resolves are continually being shattered (in 1905 as in 1895 -- or whatever that prehistoric Hill-brovian date may be) especially in the matter of letters”. Of course his use of the term "Old Hillbrovian" does not prove any connection, but the possibility of a link exists.
James Strachey was the younger brother of the better-known Lytton Strachey; both were members of the Cambridge Apostles (as was Rupert Brooke) and both were members of the Bloomsbury Group, with which Brooke was also associated. In other words, they all had unconventional sexual proclivities (Brooke himself was famously bi-sexual) that would not have fitted the mould that Thornton or Matthews wanted to steer their pupils towards. But would two wayward but (in)famous pupils have prompted Thornton or Matthews to have obliterated all past association with the school that these people attended? It seems hardly likely, especially in those pre-Internet days when access to such information was so much more difficult.
It is hoped that further research may reveal some history of the school before its Eastbourne days. It is not impossible that the school dates back to the late 19th century and that it once had Rupert Brooke and James Strachey amongst its pupils. If it were so, then it is perhaps no wonder that its boys were so strictly regulated in its later days!