A radon survey was carried out in 18 high schools located in Tenerife Island when anti-pandemic strategies were used to reduce COVID-19 dissemination during 2021. High schools were located in radon-prone areas previously identifed by the Spanish Nuclear Safety Council. Our results showed that 12 high schools presented radon activities lower than 100 Bq/m3, 5 high schools presented values in the range 100–200 Bq/m3 , and only 1 high school presented radon activity concentration higher than 200 Bq/m3.