hy jayant 

If you want to do JEE , it is no doubt a good career option. But dummy admissions in 11 and 12 is not something which I would recommend. Because school is a place which will teach you lot many things. Doing only coaching at such a age would make  the person lethargic and you might end up losing interest and motivation. I would suggest you to go to school regularly as your 12th percentage matters a lot. You cannot put them on stake at any cost. So going to school is the best option for and this study will also help you in your jee preparation. 

Good luck !!