Hi

There is no problem even if you have passed your class 12th board examination as a private student but you are not eligible for CDS examination this is because to be eligible for CDS examination the minimum qualification required is graduation so if you want to to give CDS examination need to first do your graduation, and then only you will be eligible

Also, as per  CDS eligibility criteria 2020, your age must be between 20 to 24 years to be eligible.

For detailed information go through our page the link for the same is provided below

https://competition.careers360.com/articles/cds-eligibility-criteria

Thankyou