Hello,

Study has no age. So you can complete your 12 class from NIOS or open schooling available in your state.

• Any student who wants to take admission in Nios Open school Board Registration open for 2021 October session can apply.
• Candidate age should be complete 16 years for taking nios admission in 12th Senior Secondary Course.
• You need to have your 10 class certificate.
• Original Failure/ Compartment Without Laminated Mark sheet of class 12th for TOC (Transfer of credit).
• 12th class Failed Original without laminated mark sheet or Admit Card.

https://www.niosadmission.com/nios-requirments/

You can refer to this link for more information about the eligibility criteria.

Hope this helps!!