I think in general, yes this is true. Of course there’ll be anomalies; families who are struggling but still want the best for their kids or families who are used to the nanny doing all the parenting while they focus on their high flying careers.
But in general middle class children will, as always be at an advantage.
Take our family for example. We’re probably lower middle class and I’ve spent well over £100 probably more like £200 before the lockdown on workbooks, art supplies, new stationery, books, jigsaw puzzles, a new football etc. DS has access to his own MacBook, IPad and IPhone so he can access Google Classroom and any apps. We have a printer so we can print off other resources. DH and I are both WFH so DS has had more attention than ever during our breaks and I’ve sat with him while he does his school work and I do my work. We haven’t had to worry about losing money so far. I’m a qualified teacher (although work as a HLTA directly for the council so WFH) and I’ve worked in year 6 before so I know the curriculum. I’m able to help him with maths, grammar etc and I’ve been able to help him to start on some year 7 work. I’ve researched online lessons that he can access. We have a big garden with a trampoline, football goal, different sports equipment and understand the importance of exercise and bothering to get out with DS and play with him and we’ve done Joe Wicks every morning. I prepare us all 3 healthy meals a day and provide snacks. We’ve done lots of quizzes with family and friends over what’s app video or face party etc and played more board games than ever before. I’m not trying to stealth boast, this is just how it is.
Compare that to (worst case scenario) some children who’ve been sat in front of the TV for 2 weeks already, with parents who are worried sick about money, who might be drinking/ taking drugs (or withdrawing), who aren’t able to even begin to help with school work, who don’t have access to a computer, printer or possibly even WIFI and it’s easy to see how he gaps will quickly widen.
I also agree that the 11+ scores will be skewed, DS goes this year but my sister is mainly doing 11+ work with her DD who is in year 5.