I created sections according to their graduation year. For 2016-2017, I put the K-8th graders in sections as follows:
"Class of 2017" (this year's 8th graders)
"Class of 2018"
"Class of 2019"
"Class of 2020"
"Class of 2021" (this year's 4th graders)
When the new school year comes, I leave the students in their original sections. Then, I have their classroom teachers create a new section (such as "Mrs. Smith's 5th grade 2017-2018"), we can add her students to her new section and also leave them in their original "Class of 2021" section (forever).