Not of outcome, no. That's impossible (not to mention morally dubious) and the utopian meddling that comps embody has only succeeded in reinforcing class boundaries.
The idea that comps amounted to 'utopian meddling' shows a lack of understanding of the last 40 years of educational history. There
was a kind of apologetic egalitarian position in the decision to go for comprehensives as a strategy in the early 60s - in the Labour Party, the Unions and some educational pressure groups. HOwever Labour only got the balls to go for it (10/65) by diluting this ideological position and getting a grand coalition, including industrialists and others. It was sold to the electorate in a rather mushy way - emphasising modernisation, improved economic performance and the like (rather than simple egalitarian principles). This rather messy set of priorities was confirmed by the slogan that comps would be 'grammar schools for everyone' (or something similar). After that, Labour were pretty timid about taking on local coalitions of parents and tory politicians who wanted to keep thier local grammar or 6th form - so much so that the whole project pretty much stopped around 1975 (legal challenges from Tameside etc.). And... of course, education has been in the hands of tories and nu Labour since 1979 - with free markets, competition, increased internal streaming, specialist schools, selection on 'aptitude' etc. Within the shell of something that is nominally non-selective, the reality - the
substance - has been the creation of a ne0-market,
designed to actually give the middle classes better outcomes. Hardly an 'egalitarian' project.
All of which are arguments for improving the eleven plus (and there used to be a thirteen plus to give kids a second chance) and providing more hardship money, not destroying grammar schools as a concept
Certainly the 11+ was flawed in a technical sense - flawed in ways that ensured that working class kids had a disadvantage. However that isn't the point - they were structures designed to reproduce the inequalities of an unequal society. The tripartite system was a social process - not some technicallly flawed system that could be tinkered with.
With grammars social mobility was still much better than it is now. An
LSE study has found inequality of outcome is widening, and is increasingly tied to parental income. The notion that children of unequal ability should receive an equal education is sheer absurdity; and drags everyone down to the same level. Selection by ability defines every other aspect of life; why should schools be any different?
Just on the figures, well, I personally haven't a clue as to whether the comps are worse than the grammars with regard to social mobility. But to pose the question like that suggests you are still under the illusion that comps were genuinely seeking to deliver some kind of equality. After a few attempts at liberal education in the late 60s and ealy 70s - the kind of thing that irritated the Black Papers - they were about nothing of the kind. I thinkyou are factually wrong on that. However your points about the 'absurdity' of teaching kids with different abilities are actually offensive.
It was to Crossland that I was referring:-
"Society's educational talent scouts will spot the future Bevins and Morrisons at an early age, and rush them off for training as members of the elite; and the Trade Unions will be led by the indifferent residue, and the Labour Party entirely by Old Etonians."
Or of course, ""If there's one thing I do, I will smash every fucking grammar school in the country."
The Future of Socialism attacks the notion of meritocracy, afraid that it would replace an economic elite with an intellectual elite. Of course, all comps have succeeded in doing is combining the two, and entrenching the result. You said bright working class kids who made it were "isolated" from their class. If class is what defines you, and if class war is the vehicle for a better society, then that thought will obviously repel; if class is something that should reflect ability, then nothing is fairer than redressing an accident of birth.
So, grammar schools 'redress an accident of birth'? That seems to be suggesting that being born bright and working class is odd - a kind of alien amongst an underachieving mass of thick proles. Not sure I like the tone of that.
But that aside, if you are keen to address class inequality, why not try and change the society that produces that inequality (rather than pulling out individuals and giving them access to the glittering prizes)?