Thank you for your question!
Unfortunately, you can't join it in the 2nd year of the semester. Many people are under the misconception that you do not require good board marks and only Mains marks are important. But that this is not true. You need to secure 75% to have a good chance. As long as you have that in 12th, and higher division marks in Mains, you will have a fair opportunity to get in, usually.
If you have a good grasp of your basics, JEE Mains are easy to score a 200 and above in. Try getting between 90 to 95 in your boards considering how hard the competition is. MHRD's announcement stated that if a candidate wants to take admission in any of the IIT, NIT, IIIT and other CFTIs they must acquire at least 75% in their respective boards or be in the top 20 percentile of their respective recognised boards.
You can always regive JEE if you do not get in during your first attempt so spreading out your Plan of Action, by focusing on Board marks and then JEE the next year is a good idea if you do not have enough time to prepare for JEE during your first attempt. It all comes down to your planning and your goals. What you are comfortable with and how you work is the key. If you use the system to benefit you, depending on your skill set, you will succeed.
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