With the widespread violence that has paralysed north and north-east Delhi, safety has become an issue of paramount importance. In the riots of the last few days, even children were not spared. 

Source: France 24

Keeping that in mind, the CBSE has postponed tomorrow's Class 12 English exam that was scheduled at 73 centres in north-east Delhi, and 7 in east Delhi.

The official press note on the CBSE site says, 

Based on the request of Directorate of Education, Govt, of Delhi and to avoid inconvenience to students, staff and parents, the board has decided to postpone the following subject exams scheduled for 27.02.2020.

The exams postponed are English Elective, English Elective C, and English Core. 

Source: CBSE

The next date of exams for the affected students will be notified soon. You can get further updates on the CBSE website.