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.
Usually 22 years old. Most people finish high school in the US at 18. Most BSME and also BSEE, BSChemE etc., are four year programs. So if they go straight through four years of college with no delays or detours then they will graduate with a four years bachelor degree at 22 Y.O..