Can you still attend highschool if i am 19 years old and was discharged?

Would you be able to still attend highschool if you are 19 years of age discharged and have an average of 31.00 ulative credits averaged.In NYC .I am currently in a highschool online vocational trade at jobcorps academy and I wanted to know if there is a possibilty that i would be able to receive my highschool diploma from a board of education highschool from NYC if anyone has any information that would be of any help thank you very much