K-12 school-associated outbreak: educational institution that has been found by their local health department to have multiple cases comprising at least 10% of students, teachers, or staff, within a specified core group OR at least three (3) cases within a specified core group meeting criteria for a probable or confirmed school-associated COVID-19 case with symptom onset or positive test result within 14 days of each other; who were not identified as close contacts of each other in another setting (i.e. household) outside of the school setting; AND epidemiologically linked in the school setting or a school-sanctioned extracurricular activity. K-12 school-associated cluster: An educational institution that has been found by their local health department to have multiple cases comprising at least 10% of students, teachers, or staff, within a specified core group OR at least three (3) cases within a specified core group meeting criteria for a probable or confirmed school-associated COVID-19 case with symptom onset or positive test result within 14 days of each other, AND no likely known epidemiologic link to a case outside of the school setting.