Sleep paralysis occurs as a person is moving into or out of REM (rapid eye movement) sleep, the deepest part of sleep. During REM sleep, the body is largely disconnected from the brain, effectively leaving the body paralyzed.
England and a few other countries start formal education at age 4 or 5. That's harmful and misguided.
In the 6 years that you spend in primary school, you are split between 6-8, 8-10 and 10-12 years old. Average classroom sizes vary by region but are roughly 25 students per class. Secondary school. Also compulsory and free between 12-16 years old. Secondary education is split into 4 areas, between 12-14 and 14-16 years old.