Well regardless of that you still need to get all your documents attested for all your training done towards your license/rating from both schools.
Now coming back to your question the certificate like 50 Hr Solo X-C/100 PIC etc, I would get them signed by your first school asuming you have done majority of your flying from their.
But honestly DGCA doesn't give a
which CFI attest it as long as they see a stamp and a signature on the school's letterhead there little brain is satisfied.
