Because of the deteriorating air quality, schools in many cities including Delhi, Noida, Ghaziabad and Gurugram were closed and classes are being held online. The Air Quality Index (AQI) deteriorated significantly in these cities, prompting authorities to take this decision. The air pollution levels in Delhi increased so much that restrictions under Grade 4 were imposed with immediate effect on Saturday. Initially, order was issued to close all schools except for Classes 10 and 12. However, after the Supreme Court order, schools for Classes 10 and 12 were also closed in th national capital.