hi,

see nios, national institute of open schooling is comes under recognized board of india, so students from nios can participate in neet, jee main like exams, however neet eligibility criteria is you need to have 505 marks in  physics chemistry and biology in aggregate in 10+2 course from a recognized education board, for reserve category candidates (sc/st/obc) marks criteria is 40% in pcb in aggregate.