There’s really nothing you need to do in Jupiter to close out the school year. If you want, teachers can lock their grade books on “Grades > Report Card”, but that’s not required. It is a good reminder, though, that grades have been finalized and shouldn’t be changed. (They can be unlocked if needed, to make any adjustments though.)
Here’s the help page on starting a NEW year in Jupiter:
jupitered.com/help/?newyear