Having a level of protection against freaking people out, Jeff was careless in taking over the school. Having several Jeffs to take a couple solid days to read over his textbooks was a solid investment. Getting recommended reading on additional topics was another boon. This new reality where he didn't have to choose between fun, work, school, exercise, and rest was simply amazing. Within a few weeks he was bored in his classes and asking the teachers for the textbooks handed to Juniors, then Seniors.
He got several entry level jobs which all wanted him to start at 4pm but there was only one car for the family until he could buy another, so one version of him was left home each day and it would split into however many versions he had shifts to work. He would busy himself in the morning, have lunch, and walk to work in the early afternoon.
Jeff made chores in the house and outside the house a breeze, its amazing how fast a Walmart trip can be when you have a person per item you want grabbed. And having 8-10 teenagers split the work of mowing, trimming, edging, weeding, sawing, raking, hauling, and burning really speeds things up, shockingly.
Jeff's rapid studies, spurred him on to start looking into a GED since finding the time to read all the school's textbooks cover to cover was a snap. Not to mention with his newly disposable income, a GED Prep book was well within reach. He offered to work each weeknight and double shifts both days of the weekends, swapping himself out with a fresher version of himself mid-shift while his exhausted self went home. Doing this across multiple jobs, multiple weeks and weekends, he began his nest egg.
By the time a month had passed since he had gotten these powers his birthday had receded 6 months to make him 17. His body changed but remained trim, the walking to and from shifts probably helped despite various clones needing to eat at varied times depending on their activity and all having the voracious appetite of a teen.