I'm getting quite tired of some of these threads - at the end of the day your views are going to be heavily dictated by (a) whether or not your family is currently choosing to pay private school fees and (b) the extent to which you care about social inequality and (c) if you do care about social mobility/equality whether or not you think this policy will make a difference.
We live in a democracy - if you don't like this policy, don't vote labour. If labour gets in, that is what the nation has decided so in the name of democracy you need to accept it. I didn't vote for the last 14 years of shambolic Tory governments that have certainly left me worse off. I didn't vote for Brexit. I didn't vote to have our mortgage go up by £600/month last year.
I went to one of the most expensive private schools in the country (current fees around £40 K a year). Most of the people in my year group, IMO, were not very bright at all but were given a huge leg up and contacts to get good jobs/salaries later on (or at least they had the social contacts to marry very wealthy ex-Etonians). For what it's worth I do think it would be a good thing if people from wealthier backgrounds were absorbed into the state sector. In the background I came from, I don't think parents were paying out money just for "education", they were paying to avoid having to mix with people from lower social classes. I am not saying this is true for every parent, in particular I feel for parents of children with SEN, but the social divisiveness that private schools create is not in line with my political and personal values. Sadly I don't think this policy will achieve much in terms of social mobility, schools like my old one have enough financial reserve to absorb the costs themselves.
I agree with one former poster about people not understanding that there are families, like mine, that have a decent disposable income (household income > £200 K), certainly do not live in the catchment area of a "good" secondary school but choose to use that school anyway because we don't agree politically with the notion of private education and want our children to experience mixing with students from a wide range of backgrounds - that is educational in itself.
That said, if your main value in life is trying to give your kids the very best in education, then who am I to judge? It's just different life choices. But at the end of the day this does boil down to democracy and on-going squabbling on these boards isn't going to change much.