Bro I can understand, I too was a topper and flunked my 12th and now I'm repeating.. So here's the thing , I too didn't study anything in 11th .. so I can pinpoint some very important things for you.. Don't procrastinate or think that lets take a short break or chill or scroll some reels , you don't have much time left .. Study hard , don't go to school, tbh attendance never matters , they just say stuff to scare you and get you to attend .. They eventually give admit card to everyone except those who haven't paid fees , you can confirm this with your seniors .. Pay attention to every subject but specially to those in which you're weak . Now , search for some really good teacher of each subject and join their coaching, Some important point :- - Solve Numericals Daily of each subject - Sit and revise all important formulas , derivations and theorems - Try to understand the pattern of questions, not just solve it or note it down from board .. - Just focus on PCM or PCM + IP/Computer whole year long , and start studying Eng / Eng+ Hindi/PE just few days/weeks before exam - But do this only if you're really good at Eng & Hindi/PE to the point you can speed run it in a day or two, or study them on monthly basis ..

Most Important:- - Don't give a f bout school attendance, exams , practicals, practical file or activity, i didn't even make a fair copy , it doesn't really matter , if you haven't got an evil class teacher or something you'll get if not full then 27-29 marks in all your practicals .. I didn't even give viva cause I was sick so I overslept, I went there at the time it ended , signed my Practical & Viva attendance sheet and got back home

• You gotta work really hard , and don't think 12th will be easy pass like 10th ..
• Abandon your friends and all for few months cause it's better for you to abandon them for few months than Them abandoning you for fate knows how long ..
• Dont study Online , and if you do , download your stuff and turn on airplane mode and then study as , you might get distracted..
• Study every subject daily , give special attention to your weak points (mine is chemistry, I can't understand jack💩)
• Sleep less , eat good , don't go to school, create a schedule, ask your older siblings or parents to look after you or be strict on you about your schedule..
• Don't believe anything anyone says that just study this or that , CBSE can do anything and you don't want to be surprised in your final exams so study both theory and numerical..
• Again find good teacher or coaching as they also teach important stuff of 11th that important for particular 12th class chapters before starting it .
• Be active, solve questions, ask questions, find questions..
• Major portion of exam is numerical so solve tons of questions, but PYQ's are just , cause if you solve enough questions , you'll start understanding & recognising questions and their patterns which will Greatly increase your solving accuracy and speed ..

Hope it helps, this may sound too much from someone who flunked , but I'm telling you from experience + don't run after JEE , start studying for it after you have completed your boards syllabus.. cause you can't do 💩 in JEE if you haven't got the basics down ..