Unless I have missed it you are now changing the narrative to suit your purpose.
If a child had a pen that exploded or was running out why would I punish them.
If I child persistently turns up without the correct equipment why should I provide it?
More importantly why should the child get away with it?
And before we get on to the "a good teacher would", do you have any idea of how much money a teacher spends on equipment that should be proved by by parents?
And FYI children with no equipment often use that as an excuse to disrupt the class.*
Have you ever thought why a child might not have equipment? I knew a family when I was growing up, big family think 10 plus, dad never worked nor did mum (to be fair to her she was pregnant or looking after babies most of the time). The children were underfed, it was clear as day to look at them, they wore scruffy clothes, had no uniform or PE kit. A couple of them were really good at sport but they were constantly punished for not having kit so missed out on sport. When the older child I knew started work they bought PE kits for all the kids still at school. Their lives were shit and did a kind teacher give them a glimpse of better things? Did they hell.
One of my sons had a friend who was unwanted and dumped with his grandparents when his mother married. He was a good footballer, he joined the team my son played for and the manager bought him boots, we all gave him lifts to games, included him in celebrations at McDs when they won a match. I think we gave him a glimpse of a better life.
I'm not saying teachers, or football managers, should buy kids kit but punishing them for something they have no control over?