Considering the loss of classroom teaching time due to the Covid-19 pandemic and lockdown, CBSE reduced the syllabus of classes 9 to 12 with the help of suggestions from NCERT.
The CBSE syllabus has been rationalized keeping intact the learning outcomes so that the core concepts of students can be retained.
CBSE stated in its notification that the deleted portions of the CBSE syllabus should not be considered for internal assessments or for the year-end board exams.
However, teachers should ensure that the deleted portions are explained to the students so that they can use it to connect to other topics, the notification said.
http://cbseacademic.nic.in/revisedcurriculum_2021.html