
Through a notification dated 16th of October 2019, published on the official website for the clarification on the CBSE Board exam syllabus. CBSE (Central Board of Secondary Education) clarified that the syllabus for class 10th and 12th CBSE board examination 2020 would be based only on the syllabus given by CBSE. And not according to that given in the textbooks of NCERT.

According to the notification, CBSE noticed that certain places in NCERT textbooks states that “the certain parts of the textbook are not meant for assessment and examination”. Similarly, the same kinds of instructions are given for the information and the questions which are enclosed in the boxes.
Hence the circular put a clarification on this fact and asserts that this information (as mentioned in the NCERT textbooks) is not applicable for the students who will be appearing in the Class X and XII CBSE board examination 2020.
Official link of class x and class xii board examinations syllabus
CBSE has advised to all CBSE affiliated schools and their students to go through the syllabus of class x and class xii board examinations. The Central Board of Secondary Education has uploaded it on its official website —http://cbseacademic.nic.in/curriculum.html (official link).
The notification also mentions that the examination or assessment for the board examinations will be done only on the basis of syllabus provided by CBSE and not as given in the NCERT textbooks.
CBSE also urges that this information should be invariably brought to the notice of all the concerned teachers, students of CBSE Board and their parents so that they can prepare for CBSE Boards Examinations 2020 according to the CBSE Syllabus.
Hence, we can conclude that the teachers and the students need to cross-check the prescribed subject matter from both the NCERT books and CBSE syllabus.