There are no such instructions available to re-sign the school leaving certificate by an Education Officer. You must be sure that the school leaving certificate issued by your school must have the signature of the headmaster/headmistress and the seal of the school. If you have this then you have nothing to worry about it and you can submit it for the admission in medical college.

To know more about the NEET counselling visit the link below:

https://medicine.careers360.com/articles/neet-counselling

I hope this answer helps. All the very best for your future endeavors!