back-to-school announcement, which included another $25 million to improve ventilation in schools, the Toronto District School Board (TDSB) is revealing what students will see when they return to the classroom next month.Standalone high-efficiency particulate air (HEPA) filters will be in every classroom, portable and wellness room across the TDSB in an effort to curb the spread of COVID-19 in schools.“It was something that we committed to doing last year.