Earlier this week, New Delhi's air quality index (AQI) registered a severe 427, following a peak of 461 last weekend. The Indian Pollution Control Board (CPCB) reported "severe" air quality at 27 monitoring stations across New Delhi, with 12 stations at "very poor" levels. Wazirpur recorded the worst air quality, reaching 475.

Responding to this situation, the capital's authorities required children from kindergarten to grade 5 to study from home until further notice.

Residents wearing masks move through the streets of New Delhi, India, on 15/12. *Photo: AFP*

Previously, the New Delhi administration advised educational institutions for middle and high school students to adopt a hybrid learning model, combining online and in-person classes as appropriate. Under this regulation, schools remained open, and attendance was voluntary, subject to parents' and students' decisions. This learning format will continue until further government notice.

CPCB defines AQI levels as follows: 0 to 50 is "good"; 51 to 100 is "satisfactory"; 101 to 200 is "moderate"; 201 to 300 is "poor"; 301 to 400 is "very poor"; and 401 to 500 is "severe".

Ngoc Anh (According to Hindustan Times, NDTV, Times of India)