But still a relevant reply because @Helena2022 revived the thread with very similar concerns.
I agree 100% with @mathanxiety. That sort of pressure on such little tiny kids is insane! The teacher needs to nurture, not compare.
Apologies in advance for the essay but this is just so wrong. There's far too much pressure on kids to develop at a uniform rate in the English school system.
We moved to Canada when my DS1 was turning 6. He'd been struggling with basic reading and writing in his English primary school. He basically repeated a year once we moved (he was put in a class of children who were the same age as him but they start school later in Canada) and he still wasn't excelling, but at least he was finally keeping up with his peers. The most important difference was that he loved attending school over here, with little pressure and far more play.
He jumped from struggling to read at all (finding even the easiest "beginner-reader" books very difficult) to reading chapter books in the space of about 6 months, at age 7, but it was only once he was finally ready.
The fact that he could barely read at age 7 didn't stop him from turning into a complete bookworm and winning a full tuition scholarship to do his undergrad degree. Now he has the same for his chosen grad program, with about $20k of scholarship funds left over after his fees are paid.
I'm certain that the reason he's won these awards is because of his attitude to studying (a direct result of him considering learning to be such a fun experience) every bit as much as his late developing
intelligence.
He's a sensitive soul and if he'd continued to be told that his work wasn't good enough by teachers I know that we'd have struggled to keep his confidence levels up. He could so easily have been discouraged and ended up dreading going to school... 
They're tiny little kids, not robots 