Hi there.

To be eligible to write NEET one has to be 17 years of age with at least 50% ( for UR category) aggregate marks in class  XII boards with Physics, Chemistry, and Biology. So, yes if you want to write the NEET examination, you can surely write Class XII examination from an open school with Biology as well as Physics and Chemistry.

Click the link below for more relevant information: 

Https://medicine.careers360.com/articles/neet-eligibility-criteria

Hope this helps.