Fort Caroline Middle School students will start their day Thursday by logging onto their computers. The school announced Wednesday that it would switch to online instruction until Monday, citing "multiple" COVID-19 cases. "Because of the number of recent cases and the impact on our school, we will transition all students to online instruction through Duval HomeRoom," Principal Chelvert Wellington told families. "My team and I stand ready to help make this transition as smooth as possible." Duval County Public Schools has closed schools and transitioned them to temporary virtual instruction before. The district uses a 20 percent impact threshold to determine when the switch to online learning should happen. That threshold measures how many students and faculty are impacted by COVID-19 exposures — not necessarily that 20 percent are COVID-19 positive.