Legacy system. Someone once started curating two spreadsheets for each year because they didn't know better. They had different formats too, because the naughty one listed separate entries for each naughty deed and a column describing it. Whenever they added something to that list, they manually checked and deleted the kid from the nice list.

Eventually, the amount of children they're responsible for got too large, so they learned some basic SQL and built themselves a database. To import the legacy lists and keep their workflow, they built separate tables. Just be glad they eventually learned how to filter by year and stopped creating new schemas for every year.