Online learning is fraught with problems. I'm sure your grandchildren did just fine as will many other children. But many will not. Multiple studies have been done into virtual learning in this time and the findings are clear - online classes increase the gap between the smart students or those from good families and the ones that struggle and/or are from disadvantaged ones. The better off students who are self-driven and academically minded will cope with virtual classes, often supported by parents who are willing to assist them in their school work and by access to good internet connections, books and other means of learning. But disadvantaged students will struggle even more than previously due to lack of focused assistance from teachers who are less able to cater to their needs in an online environment, difficulty in accommodating kinesthetic learners, significant differences in quality between teachers as to their effectiveness and training in delivering online classes, deficient internet and resource access amongst poorer families, and having parents that either can't or won't supervise and assist their learning and will leave them to struggle or not pay attention to their school work at all.
In short, online learning tends to increase inequality in learning outcomes and is highly likely to leave many students with gaps, deficiencies or disengagement in their learning that they will never recover. A significant number of those students will be from poor families and minority groups. Then there are the mental health and socialization challenges for children who are not able to play, interact, work and compete in sport with their peers and who are experiencing intense disruption to their routines and sources of enjoyment, which can have significant short and long-term effects.
It is not easy, I freely acknowledge that. There are immense health challenges with sending children to school during a pandemic. It may well be in some places that the health impacts of doing so are even greater than the negative impacts on learning, so virtual classes are indeed deemed necessary in those locations for a time. But that decision should never be made lightly and it must be made with full awareness of this fact - online learning will hurt some children and damage their prospects wherever it is enacted, no matter how well it is done.
Studies:
https://www.dese.gov.au/system/files/doc/other/lamb_-_impact_of_learning_from_home.pdf
https://www.dese.gov.au/system/files/doc/other/learning_at_home_during_covid_30042020.pdf
https://www.dese.gov.au/system/file..._and_vulnerable_children_acer_22april2020.pdf
https://www.dese.gov.au/system/files/doc/other/clinton_supporting_vulnerable_children_final.pdf
https://www.dese.gov.au/system/file...iew-learningathome-covid19-final_28042020.pdf