Child (age 7) completes some work, teacher asks who would like to read theirs out, child volunteers, teacher looks at work, sighs and then says "you can't you haven't done it right". Then proceeds to rip page out and tells child to start again?
DS1 (who is dyspraxic) had a maths teacher who used to rip hs work up because it was untidy. It was horrendous, bullying behaviour intended only to humiliate DS1. And completely pointless, because it means there's no way of looking back and showing him how he has improved in future, etc.
Sadly this is a true story. And the teacher thought that ripping up a child's work in front of the class was a perfectly reasonable thing to do.
When I complained about it, the (allegedly 'outstanding') school just put DS1 in the bottom maths group and stopped teaching him anything at all. He spent the rest of Y5 learning the 2 times table, and became worse at maths than he had been when he started at the school in Y3. (You might not think that so bad, but changing schools came with an incredible improvement in all aspects of learning and he went from levels of 2/3 to level 5s in his SATs in the course of Y6 alone, purely because the school actually taught him. DS1 is actually very good at maths and is in the top set in Y8).