i am principal, assistant principal, teacher, paraprofessional. i cover classes, lunch recess duty. i do everything that needs to be done. reporter: and in thirdad neeu gu to write t your blue n, please. reporter: she usually works in the district s main office. in the denver district, superintendent alex marrero tlls us everyone is doing multiple jobs. it s in droves that we re having absences. reporter: the pool of substitutes has plummeted amid covid fears from 1,200 to just 375, not enough to cover those out due to stress and illness. it s not just here in denver. burnout is fueling shortages of teachers and staff, like bus drivers and cafeteria workers, in schools all across the country. principal joseph uy vacuums his las vegas elementary because he s short on cleaning staff. he s also teaching.