For a foreign public document to be accepted by Greek public services, it must first be duly authenticated on a case- by – case basis. Authentication precedes its official translation. 

A) If the foreign public document has been issued by an authority of a country which is a party to the Hague Convention of 1961, it must bear the apostille stamp.

A1) The apostille stamp must be set on the original genuine documents (original degree, undergraduate diploma, etc) and not upon a copy.
For the list of countries that are parties to the Hague Convention of 1961, see https://www.hcch.net/en/instruments/conventions/status-table/?cid=41
For the list of institutions in each country responsible for the affixing of the Apostille stamp, see https://www.hcch.net/en/instruments/conventions/authorities1/?cid=41
Nowadays, in most of the countries there is an electronic apostille issue service (eApostille). Please try to use this service if available in your country region. It will speed up the verification of your document and eventually your enrolment.

A2) Once stamped, the documents must be officially translated into Greek by an official translation service (see below).

After the set of the apostille, genuine stamped documents (originals, not copies) together with the genuine Greek translation of them, must be kept available in any case the Secretariat of the School might inquire them.

B) If the foreign public document has been issued by the authorities of a country that is not a party to the Hague Convention or, of a country that although they have acceded to the Convention, Greece has expressed objections (i.e. Kyrgyzstan, Mongolia, Uzbekistan, Peru, Tunisia, Philippines, Kosovo, Pakistan), the steps that have to be followed are:

B1) Certification by the Ministry of Foreign Affairs of the document’s country of origin

B2) Certification by the relevant Greek consular authority in the country of origin. IMPORTANT: Make sure you keep safe the “Proof of Receipt” issued by the Greek consular authority, upon completion of certification. You must send it to us for an easy and quick way to verify the certification and complete your enrolment. If you lose the “Proof of Receipt” the final verification of your documents has to be made by the service of the Ministry of Foreign Affairs called “CITIZENS AND GREEKS ABROAD SERVICE AND INFORMATION CENTER”. Please visit their webpage, if needed, to see their contact info. Their webpage is a source of information where you can be informed thoroughly about which case you are subject to. 
Exception: Documents coming from Ethiopia, Algeria, Afghanistan, Ghana, Eritrea, Indonesia, Iraq, Iran, Kenya, DR Congo, Libya, Mali, Bangladesh, Nigeria, Pakistan, Senegal, Sudan, Sri Lanka, Philippines and Tunisia, are certified only through the competent paid Greek Consular Authority.

B3) Once verification completed, the documents must be officially translated into Greek by an official translation service (see below).

CAUTION: Appointments to governmental services either Greek consular authorities or Ministry of Foreign Affairs of the country of origin might not be so timely fixed. So, plan as enough ahead as possible to prevent missing the enrolment deadline.

Genuine stamped documents (originals, not copies) together with the genuine Greek translation of them must be kept available in any case the Secretariat of the School might inquire them.

SERVICES AND BODIES CARRYING OUT OFFICIAL TRANSLATIONS INTO GREEK LANGUAGE

1. Paid Consular Authorities of Greece (Consular authorities are divided into paid consular authorities, which are headed by officials of the Diplomatic Branch, and unpaid consular authorities, which are headed by honorary officials )
2. Τranslators cerified by the Greek Ministry of Foreign Affairs, search here: https://metafraseis.services.gov.gr/
3. Greek lawyers that certify their proficiency of translation from the original language to Greek language.

Νo other source of translation is acceptable.