There's nothing racist in adhering to uniform policy.
There is if the policy is ridiculous and racist.
Posting stuff from a quick Google of schools in Nigeria isn't the same as a proper comparison by the way. To be honest, there aren't many parts of the Nigerian education system I think we ought to adopt - but in particular daft rules about hair would be low down the list. Not sure why you think it's in any way relevant to school in London.