Hi
I do not think u would be eligible for IIT JEE . The 12 board exams are the qualifying xams fr IIT , and u din appear fr that. 
Fr JEE 2009, the foll were the eligibilty criteria:
1. He/she can attempt JEE only twice, in consecutive years.
2. He/she should have passed (10+2) or equivalent qualifying examination in 2008 or should be appearing in 2009, and secure at least 60% (55% for SC/ST and Person with Physical Disability PDI] marks in aggregate in his/her respective Board Examination. He/she should NOT have passed the qualifying examination earlier than October 1, 2007. If any Board awards only letter-grades, he/she should obtain a certificate from the Board specifying equivalent percentage marks. In case the respective Board awards letter-grades without providing norms for converting them to equivalent percentage marks, the norms decided by the Joint Implementation Committee, JEE-2009 shall be final.
3. He/she should NOT have accepted admission by paying full fees at

any of the IITs, IT-BHU- Varanasi or ISMU, Dhanbad through JEE.
4. He/she should have been born on or after October 1, 1984 (October

1, 1979 for SC/ST and PD candidates).
So, u need to do 10+ 2 to  appear fr the xam.