I have always been against grammar schools because they can ruin the education of the majority who would end up in secondary moderns, with possibly little incentive to do well due to peer pressure.
A well set truly comprehensive school with opportunities to easily change sets each year is surely the best option for all children. Not streamed, which means the same stream for every subject, which puts those with spiky profiles in the wrong stream. i.e. Child excelling in maths but struggling in English, what stream to put them in. No, setting by individual subject is much better.
My DS3 is top set for maths and science, middle set for English, bottom set for games. He actually enjoys games now!
I think there may be an argument for a small minority to go to a super selective grammar, if only 2% or so, because that top 2% could be seen as having SEN very different from the other DC and it wouldn't have much effect on the comprehensive schools.
However, grammar systems where the top 40% or so are removed at 11yo just destroy the opportunities for the other 60%.