If the nanny is really 'raising a child' because s/he is there for 10-12 hours per day for about 3 years of a persons life then I question whether fathers who go out to work and arent there during the day are really raising their children? Can they really call themselves a parent?
10-12 hours a day is c.90% of their waking hours, and unless youre Paul McKenna you'll have a job exerting parental influence when they're asleep, so I don't think you can dismiss the fact that if a child spends the large proportion of their awake time with AN Other then that person will have a significant influence over that person, their behaviour, their values, language development, etc. If we didn't believe that was true, then we wouldn't invest so much time in selecting childcare. It's not that working parents aren't parents, but lets not pretend that the person who is the primary carer (i.e. the nanny) is not going to have a significant influence, because they absolutely will.
Ditto the comment on schools. Parents absolutely do believe that the school their child attends will have a massive influence on their life outcomes so to an extent, yes, the school will raise my child. I'm down with that.
Finally, SM, please get over your obsession with Ofsted. I've seen Ofsted regulated establishments that I wouldn't trust with my dog, never mind my child. Children with shit parents or parents who don't really enjoy looking after pre-schoolers will probably be better off in daycare or with a nanny. Children with very invested, interested, bright parents will probably be better off with their parents. It's not a one-size-fits-all thing.