The eligibility criteria for Karnatak State quota seats are:

• He/she must have passed Class 10 and Class 12 from an institute located in Karnataka. Also, he/she must have studied for a period of seven years from a government school located in Karnataka

or,

• He/she must have passed Class 11 and Class 12 from an institute located in Karnataka. Also, either of the candidate’s parents must have studied for a period of seven years from an institute located in Karnataka.

or,

• Candidate and either of his/her parent’s mother tongue is Kannada/Tulu/Kodava. Also, this parent must be a domicile of Karnataka state.

Now as you have done your education about 16 years in Karnataka then your son is eligible for the state 85% quota seat in Karnataka.

I hope this might help. All the very best for your future endeavors!