Equality of Outcome: why?

[mmzz]

I genuinely don't understand why anyone would believe that equality of outcome is what schools should be optimising on. To me, the fair thing is equality of opportunity.
Please can some tell me why equality of outcome is fairer or better in any way, even economically for the country?
Who does it help? Who does it hinder? Is that fair or good?

Thanks GHGN that is really good advice. I appreciate your taking the time to offer it.