This is basically an alternate version of the original Millard High RP, like the Genderbend RP. All the big, burly Millard High students have been downsized into little elementary children. KUMBUYA!
If your character was a freshman in Millard High, they're a 2nd grader in Millard Elementary. Sophomores will be 3rd graders, Juniors will be 4th graders, and so on. You can go ahead and include younger siblings or maybe even new, original characters in the lower grades if you so wish (Pre-K, Kindergarten, and 1st grade). Most (maybe not all) people aren't exactly the same as they are in elementary as they are in high school, so maybe you want to change your character's personality a bit or at least make them a little more naive.
Unlike Millard High, Millard Elementary, will have recess...oh, and nappy time at the end of the day? lolidk. Teachers will be more or less the same (or if you guys want, we could make new, original teachers), but I think there should probably be less subjects. Ayup.