Why does my child shut down when they make a mistake?

What people tried

Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.

1. 1
   telling the child it is okay to make mistakes and that they are learning
2. 2
   modeling making mistakes and talking through them positively
3. 3
   Giving the child a snack break to prevent hangry meltdowns
4. 4
   Asking the child to walk through the problem step-by-step or double-check their own work instead of saying they are wrong
5. 5
   Using answer keys so the child can check their own work first
6. 6
   Taking a step back, letting the child work independently, and leaving grading or error correction to the teacher
7. 7
   Giving the child time to cool down before trying again

In their words

Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.