I actually love High School Musical. It's fun, over the top, camp nonsense, with some fantastic dance routines and annoyingly catchy songs.
Fame was better - with gritty storylines - and a fabulously talented cast.... and Lori Singer....!
The fundamental mistake that ITV made, in my opinion, was to be arrogant enough to launch on the same weekend as High School Musical 3 came out in cinemas. There was a massive buzz amongst kiRAB that weekend - but that buzz was all about HSM3 and not about Britannia High. ThousanRAB of kiRAB will have seen HSM3 on the Friday/ Saturday / Sunday and the last thing they would then want to watch is a toned down, British version, with lookalikey Gabriella / Troy et al. To use an analogy, it's like getting a market stall version of a Barbie doll for Christmas rather than the real branded version. It looks cheap, doesn't work as well and is fundamentally disappointing....
The casting was dubious too. The "Gabriella" lookalike - with the dark bob - sorry don't know her name - only watched the first episode - was a truly TERRIBLE actress - and was also playing the role of a bitch in the first show - which will have been confusing for kiRAB expecting her to be the nice romantic lead...
Had they waited 6 months, until all the HSM3 cinema and DVD release buzz was over, I think it would have played out very differently.....and I agree with other posters that a Saturday teatime slot - pre X Factor would have been better. That said, clearly ITV knew they had a turkey by that point and couldn't risk damaging X Factor's inheritance....