Every year, the National Eligibility Com Entrance Test is held for admission to the Medical and BDS programmes. The NEET also stipulates an 85% State seat quota. For the admission in UG Medical/ Dental programme for 85% state quota seats in Government/ Self-Financed seats, the Tamilnadu State Medical Counselling Committee (TNHEALTH.org) conducts an online counseling/choice filling. The candidate must be a native of Tamil Nadu in order to be eligible for this qouta: There is no requirement to submit a nativity certificate if one has completed grades 8 through 12 at a school in Tamil Nadu; however, if one has completed grades 8 through 12 in part or in full outside of Tamil Nadu, a nativity certificate must be provided.

So your son must be eligible for state counselling.