State Schools VS Grammar Schools

Hi guys, this is my first post on here and I'm not too sure on how this works so I hope I'm doing this right lol.
I currently attend a state secondary school, and have received offers from two private grammar schools which have both offered me a conditional place at their sixth form, however, I'm not too sure about whether or not it's worth going and spending all of that money on a sixth form that may just be like any other. I mean don't get me wrong, both schools A-level results are far above the national average which is great but what if the reason why their exam results are good is because the majority of people can afford to get private tuition?
So yeah my main question is, is the quality of education and support provided at private grammar schools truly 'better' than those provided at state schools? Or are the students just naturally academically talented?

I was in the same predicament as you however I also factored in the fac