The world is a lot more complicated since Precocious Puberty became a very real thing. It started in the 60s. A few cases sprung up here and there. Young boys who were very large. Five year olds who were the size of ten year olds. They couldn't play with kids their own age. Psychologists spent years trying to help them. As they matured, they matured quickly. 8 and 9 year old boys were learning to shave. And by 10 or 11, they began to resemble 18 to 21 year olds. This hyperacceleration could not be explained, but typically the aging process tapered to a normal rate once they reached a physical age of 30 or so. Typically, a precocious puberty case could look anywhere between the ages of 25 and 35 by the time they actually reach college.
They began to call most of these children "Skippers" as an affectionate reference to the fact that many of them could fit in easily into the adult world. Just as some students skip a grade or two due to their increased ability and intelligence, Skippers matured to a physically adult level much earlier than other boys.
All scientists agreed after a while that whereas one would think the bodies of such cases would be deteriorating rapidly, the physical aging was mostly external. Body hair, wrinkles, stubble, height, and early sexual reproduction ability came with precocious puberty, but the body remained largely the same as its linear age. The diseases of old age would not actually affect them until old age. In fact, it appeared over time that most of them were almost impervious to diseases which ravaged others, and many vaccines were found due to their special genetics.
But then, the few isolated cases became more and more common. By the 1980s, 5% of all boys under the age of 13 resembled male adult men. By the time they hit college, they look to be about the same age as their dads.
Over time, the rates increased slowly until they started tapering by 2010. Today, 15% of the male population has Precious Puberty. They are allowed MOST of the same privileges as adult men. The ability to act your age has become an art form with many classes in the subject. Many special schools operate to teach boys with precocious puberty how to act, behave, and live their lives as adults. Many of them have a higher than average intelligence and most pass equivalency tests to finish school early, so that they can go onto careers that they are able to start earlier as a result of their newfound adult status.
Society has fully accepted these changes. Boys with Precocious Puberty are expected to act as any adult man would be expected to by the age they look it, which is about 10 or 11.
But society treats them as equals. So that means they have the same burdens such as being emancipated early upon their request: and that means holding down a job and paying rent or going through higher education.
Though it should be said that there is no law that says Skippers with Precocious Puberty can't stay in school alongside their friends. They will look to be as old as their own fathers by the time they will graduate from high school, or if they are lucky, their mid 20s, depending on their genetics. It's a personal choice, and society usually encourages them not to linger with their own genetic age group until they hit 18, there has also been increased resistance to this. Starting in the 90s, this group became more outspoken, saying young boys that look like adults shouldn't be asked to leave school, and they do better when they aren't trying to make rent on their own or carry on adult relationships. It was strictly taboo for young Skipper boys to date girls or boys their own age. It had become normalized for Skippers to date adults, either male or female.
As far as muscle growth goes, Skippers tend to react much more quickly and grow muscle more quickly than regular men. However, they do have to do the work and do the hard lifting if they want to bulk up. It is common for Skippers to start lifting weights as early as age 9 to see much increased muscle.
Let's follow someone from this universe now. You decide you want to follow: