Eric approaches the fountain the next day to drink some more water, and as a result, Eric slowly grows back to his fifteen-year-old self, and assumed that he would resume his teenage life. But as Eric walks into the high school, his mother fills an empty bottle with the rejuvenating water from the fountain. She filled the bottle with enough water to make Eric ten years old again. This time, she also ordered the school to disassemble the fountain so Eric will stay his own age. Eric's mom then thought "When Eric turns ten a third time, he's so grounded!"
Meanwhile, Eric decided not to use any more of the water fountain because he does not want to have anything to do with the fountain and growing younger. However, while he was gone, some of his friends used the fountain and ended up growing more muscle or growing way taller. While Eric was at gym, his mother secretly switched Eric's water bottle with the bottle filled with the fountain water. However, she accidentally forgot to take Eric's regular water bottle, but by the time she found out, she was too late, and Eric was already in the changeroom.
What Eric saw in front of him are 2 water bottles; the regular one, and the one with the fountain water (although he doesn't know that). Eric drank the regular water and decided to drink from the second bottle when he got home from school. When he did so, Eric shrank again, back to a ten-year-old boy when his mother told him that she wanted him younger because it would be less work tolerating a ten-year-old than it would tolerating a teenager. She also advised him not to bother drinking from the fountain the next day because the school had rerouted the water system so the fountain no longer has any body-changing effects when anyone drinks it.
After the lecture, Eric looks at himself in the bathroom mirror, and sees his ten-year-old self in the mirror. As he looks into the mirror, his mother tells him "Eric, take a good look in the mirror, because that's how old you're gonna be for the next five years. That means you will spend the next five years a fifth grader, a ten-year-old, and grounded! For the first four years of your punishment in your ten-year-old body, we will ensure that you skip enough days and miss enough homework assignments to repeat the fifth grade!"
The story concludes with Eric going from 9th grade to 5th grade to 2nd grade to 9th grade to 5th grade for the next five years. As of today, Eric is a ten-year-old boy (which is what he will be for 5 years) by punishment, which appearently he suddenly enjoys being for five years while all of his friends advance in life. Eric is now a boy, and there is nothing he could do about it anymore.