One of the most famous junior testing astronauts was a 14 year old boy named Kevin Kelly. He and groups of dedicated youth tested the limits of survival in a space capsule and led the way to our landing on the Moon. This October 30, 1968 story in Current Science the outlines these heroic efforts. Unfortunately this coverage was limited to a newpaper distributed in classrooms so few recognize this hero today.
Kevin spent a grueling 336 hours in a test capsule in order to prove that the human body was capable of a flight to the Moon. By locating the expensive test apparatus in the basement of a suburban house they were able to avoid harmful media exposure during the testing.
Furthermore these brave young men built their own test apparatus and capsule from scratch in order to spare the Apollo funding program from further overspending.