It is unreasonable but I understand how difficult it can be at times.
Our school has said something, anything, is better than nothing but don't beat yourself up over it.
I have 4 DC, inc 2 with SEN. It can be a battle some days to get them all to do the work the school has asked for. It can be a battle every day to get the SEN 2 to do any of their schoolwork. Which sometimes leads to wails of 'it's not fair!' from the youngest.
There are ways of encouraging learning without it being sat at a table and death by worksheet.
Find the child's interests and build learning around that. Baking can include maths - weights and measures, fractions, adding and subtracting. Being in the garden - the science of growing things, what do plants need to grow, do they know the names of the plants, their parts. The creatures that visit their garden. Can include maths - make a simple chart of all the insects they have found. Grow a sunflower, measure and record every day to see whose is growing faster.
Write to friends and family - ask them to write back so there can be 2 way dialogue but also comprehension, understanding what someone else has written to them.
Share a book with them - read to them and ask them to read to you. It doesn't matter if it's a comic book.
Right now, if you can't get them to learn new skills, at least encourage them not to fall behind in others. Even if it is just as @Grasspigeons says and is as simple as getting up, dressed and ready for the day each and every day. Mine are allowed to have a pj day at the weekend but are firmly discouraged from that during the week as we have previously had battles getting the 2 SEN DC into school. I can carry the 9, nearly 10 year old over my shoulder still. But it's not something I wish to go back to when all this is over.
And also remember, this is crisis schooling. This is us doing our best to make sure our children don't forget everything they have already learned. The argument about them doing nothing for 6 weeks is an absurd argument imo. With the long summer holiday, we know it is coming to and end and when. Right now we don't know when this will end or even how our children will return to school.
Keep in contact with your child's school to let them know how you are getting on, even if it's a once a week email to say X was achieved successfully but Y wasn't and this is why.
I am in regular contact with my sen DC's teachers through the various platforms and emails they are using. Just so when this does come to an end, there isn't a shock to the school as well as to the DC.