I've heard of kids having difficulty who finally got it with things like "I know the answer so it's OK if you don't get it right", and "do you think it could be 100?"
I'm fine with those sentences, as long as it's not the only input the child gets. The first makes clear the answer was wrong. Making clear that it's not worrisome that someone learning to add still doesn't add right it's ok. Should be obvious, and the learning setting should make it obvious, but anything is worth repeating if it's not clear. The second does not make clear the answer is wrong but it's still a maieutican way to prompt the student to keep thinking and maybe find what's wrong himself (or at least give the teachers hints on how can he help him).
But it cannot be left at that. The teacher should teach how to add, not only that it is 4 (after the student had time to think, without giving away the answer too soon), but also why it is 4 and how can one find the answer in all cases. I've heard from pedagogues the children should not be taught that, they should be motivated to find the answer on their own. I know the learning process is stronger if people discover things themselves, but we don't have time to discover all knowledge the humanity has ammassed across millenia, so the most basic part should be facilitated piecemeal and properly so that modern humans can use what ancestors learnt and don't start from zero. They also say that the teacher should never say the child is wrong. I think it's important to let facts clear. It's not bad to give a wrong answer, but there are right answers and wrong answers, pretending they're all right does not help the student learn, only confuses things further (for both the student that got it wrong and the other student that got it right in his head and now would doubt it).
As a student I like it when the teacher starts by exposing some content in a relatively abstract, descriptive or narrative way, then gives examples of how to apply that content to some cases or solve problems, and then lets me solve similar exercises myself. If it starts the class with the exercise I should solve with something I haven't been taught yet, or simply accepts anything as a solution, or has students, who by definition still don't know the subject, teach each other, or correct each other, then I feel we're wasting our time.
But OK, sorry for ranting. This is not COVID related.