Hi there. 

Unfortunately no. If you haven't passed Class XII boards examinations then you cannot write the NEET examinations. 

The eligibility criteria itself mentions that 50% aggregate marks (for general category) in Class XII boards with Physics, Chemistry and Biology is compulsory for being able to write NEET considering that the candidate is between the age range of 17 years- 25 years. 

For checking eligibility criteria for NEET kindly refer to the following link: 

https://www.google.co.in/amp/s/medicine.careers360.com/articles/neet-eligibility-criteria/amp

Hope this helps.

As per the eligibility you should have minimum 50% PCB aggregate score in class 12th as a General category & 40% as a reserved category to apply for NEET Entrance Exam. You can check the further eligibility with the given below link.

https://medicine.careers360.com/articles/neet-eligibility-criteria

Good Luck!