From what I know of the School from my teacher friend, its not the high ethnic majority, but the nature of that majority as being a high proportion of refugees, therefore lots of kids with extremely troubled backgrounds & behavioural problems as a direct result - the last girl I had on work experience had 6 younger siblings, her Mum was dead, killed in a war zone & at only 15 she was now Mum to her siblings & wife to her Dad -
she cooked, cleaned & brought up the younger Kids :( as was the norm in her culture, she was a very bright & talented kid with dreams of what she really wanted to do with her life & very capable she was too, but sadly it was unlikely she would fulfil any of her dreams, due to her background - I got the impression that she was pretty typical of a lot of girls there :(
Also the violence angle, kids coming in from war zones, used to carrying machetes & fighting for there lives, so the usual kids squabbles could & often did get out of hand, craft knives held to throats etc weren't uncommon.
The oftsted will be good as the impression I got was that the teachers really DO care & work REALLY hard to give these kids the best chance they possibly can, I know my friend certainly did & ofsteds work on how much the kids improve during there stay in a School, so it doesn't necessarily mean good exam passes etc, just a big improvement from where they started - which was WAY behind most other kids - like I said some years back, but relatively recent history