I don’t think it’s quite as straightforward as others are making out.
We’re nowhere near as far in miles from ds’ grammar, but in journey time it’s not dissimilar. In the morning we drop him at the train station (five min drive) for 7.44 and he gets the train (20 mins) then a tram (12 mins) then he either walks the 15 mins to school or he jumps on a bus. On the way home he prefers to take two buses instead, which takes over an hour, because his friends are on the first bus.
The journey is tiring for sure and I wish he was nearer school. However for his personality - previously bullied,then home educated for year 5 and 6 - I know the grammar is a better fit. Also, our local schools are quite rough and have very very poor value added scores, so our alternatives are particularly bad.
Maybe for a different child or with different alternatives, we might make a different decision. So do consider these things.
Also - the journey time can be fun social time, which is why ds takes the bus after school. Also consider when your grammar school finishes - fortunately ours is at 3, so even when he stays for an hour after school hes still not back too late.
For both my children, bus/train friends have been positive. My dd has travelled with 2 other girls on the train (shorter journey though) and they’re firm friends now, meeting up for local shopping trips etc. I think kids can make ‘convenience’ friends even if they have other friends at school - it’s a life skill isn’t it to get on with the people you’re thrown together with?
Also, both my children have local friends from outside school to see at weekends - this is something to encourage even if your children are at local schools.