Any information about the document must be confirmed at school. It is built into the system itself. Fraud is possible if there is collusion with a school employee.
Fraud is possible in different stagers. That is why usualy scools double all the documents. They have a computer version of documents and paper version.
I think there are more fake diplomas than scool certificats. And I think there are a lot of fake sertificats of different courses for example from automobile scools to get car drive licences.