Personally, I wouldn't contemplate a journey over 45 minutes to an hour one way, for myself as a daily commute and certainly not for my kids. In my opinion it is not fair on the child as, regardless of what parents believe or agree or promise, that child will not be able to participate fully in the school day/life.
The transition from Y6 to Y7 is well documented as being one of the toughest transitions in a young persons life - the school day is longer any way, they will have on average an hour or more of more challenging homework a night, they have to make new friends, learn new subjects, meet new teachers, work out the geography of the school, get on a bus - often for the first time, be with lots more children of different ages and backgrounds and be the bottom of the pile rather than the top of the heap (ie bottom year in big school, rather than top year in primary.)
And that is not factoring in being at a GS - that is, the above applies to any school. And I haven't begun to list the lunchtime clubs, the after school clubs - things that are expected of them, not just the things they want to do - the friendship groups, the parties....all these things happen - but if your child has a long journey at the beginning and end of the day, they will be exhausted - literally exhausted - and won't want to, or won't be able to, get involved fully.
Remember, it's JUST a school. A bright child, with the right support will do well anywhere. A bright child who is constantly exhausted may well not.