I grew up in IL. A gal I knew as a youth retired at age 48 from a teaching career. She and her husband were both public school teachers, retired under age 50. Their combined salary from about 2014 was close to $200,000. I expect their lifetime pensions are a good percentage of that figure.
I suspect she didn't actually retire at 48, but deferred it until 55. The only way to retire before 55 that I know of, was 30 and out. New hires can't retire before 67..