My grandaughter was due to start school at the beginning of the pandemic, but obviously didn't.
For parts of the day, she had online schooling, where all of the class came together and were given tasks to complete within a specific time frame
The pupils had to log on at 9am each day, to ensure all were engaged and parents of those not engaging were contacted and offered support and equipment if necessary.
Fortunately, or not I was shielding and due to my former career, I was able to work with her each day on phonics and maths activities. She now has an above average reading age. It does not seem to have had a detrimental effect on her, academically nor socially.
I purchased the phonics materials, which she would have been using, which enabled continuity when she did start school.
I appreciate not everyone could afford the time or finances to do that.
Don't tell anyone, I was very familiar with those materials but was sick of of the sight of them, by the time she was able to start school. I thought I had seen the last of them, when I retired!
We broke up the Zoom sessions into sections and DH would take over and read and talk to her, which also maintained our relationship with her.
My DIL was an optomotrist and had to work, my input and that of my DH allowed my son to work from home, uninterrupted.
However, I do know of a number of children, due to start school last year, who were deferred. They had missed out on being at nursery and were just not mature enough to start school.