Dear Aspirant,

Hope you are doing well

The CBSE board and JEE Main are different. They are no connection between them since the formation of NTA. So the syllabus reduction in CBSE has no relation with JEE. JEE will always have the same syllabus even if the topics are not taught by board. So reduction in syllabus for JEE main is highly unlikely. '

If the topics are not taught in school , you should study them by yourselves.You can take the help of our courses or  youtube. You should also give regular tests . So buy test series also. It will help you for the main day.

Hope my answer helps.

Best of Luck for your future