There are some strange views coming through here!
Motivated kids at state schools may well be fine. Some of the brightest kids at state schools will have found this period where they can move at their own pace and get more of their work marked than usual really good as most schools have mixed ability classes in sixth form which can move frustratingly slowly.
The vast majority of state school kids are not very self-motivated, particularly boys. My Y11 DS (predicted all 7/8/9 for GCSE, so bright and works well at school) has done almost no school work for the last 2 months (sleeping, gaming, working out). Y11 are in a strange position, but parents of DC in other years have not mentioned any on line lessons at all. As other posters have said, whether any work is done is largely dependent on parents. Friends with DC at private schools have full day timetables, even including registration, so they are keeping the work ethic going and must be making more progress than the majority of their state school counterparts.
State schools here were due to break up 20/7 where we live. There should have been 192 days of school in the year (after training days and bank holidays). Of those 121 were up to and including 20/3, 72 were post school closure. So those in the non-exam years have lost 37% of the school year face-to-face. As another poster mentioned, most of the syllabus is generally covered by Easter of Y13, so the home-learning time is around 30% of the whole course time in a normal year.