This is the problem.
In normal, pre-Covid times, schools are not good places for some children. Bullying, the chaos/sensory overload, lack of SEN funding and support, behaviour of others in class disrupting learning for all, peer pressure, rigidity of curriculum and rules, exam pressure.
In lockdown times, lack of school is not good for many children. Cold, crowded, unheated homes with no food, lack of IT, lack of quiet, abuse, lack of socialising, lack of support from TAs or pastoral team, no access to reading books, no exercise
In school open scenario but constant disruption due to the pandemic and no mitigations in school the situation is not great for many, many children: illness circulating, worry about passing on to relatives, no consistency of who is teaching you, worries about exams possibly cancelled again, pressure to catch up, behaviour is MUCH worse so disruption for all and especially for those with sensory issues, rigidity and other needs.
It's not exactly as if one situation is infinitely preferable to all others. Children are suffering in all three scenarios.