Legalization of your educational documents (secondary school leaving certificate and higher education diploma) is a formal verification of their authenticity. If a country in which a given document was issued is not party to the Hague Convention, the document’s legalisation for use in Poland can be done at a Polish consular office in that country.
Afghanistan, Algeria, Angola, Bangladesh, Benin, Bhutan, Bolivia, Brazil, Cambodia, Cameroon, Canada, Cape Verde, Central African Republic, Chad, Chile, China (excluding Special Administrative Regions of: Hong Kong, Macao), Congo, Costa Rica, Cuba, Dominican Republic, Egypt, Ethiopia, Gambia, Ghana, Guatemala, Guyana, Haiti, Indonesia, Iran, Iraq, Ivory Coast, Jamaica, Jordan, Kenya, Kosovo, Kuwait, Laos, Lebanon, Libya, Madagascar, Malaysia, Mauritania, Montenegro, Morocco, Mozambique, Nepal, Niger, Nigeria, North Korea, Pakistan, Palestine, Papua New Guinea, Philippines, Qatar, Rwanda, Saudi Arabia, Senegal, Singapore, Somalia, Sri Lanka, Sudan, Syria, Taiwan, Tanzania, Thailand, Togo, Tunisia, Turkmenistan, Uganda, United Arab Emirates, Vietnam, Yemen, Zambia, Zimbabwe.
Albania, Andorra, Antigua and Barbuda, Argentina, Armenia, Australia, Austria, Azerbaijan, Bahamas, Bahrain, Barbados, Belarus, Belgium, Belize, Bosnia and Herzegovina, Botswana, Brunei, Bulgaria, Burundi, Cape Verde, China (Special Administrative Regions of: Hong Kong, Macao), Colombia, Cook Islands, Costa Rica, Croatia, Cyprus, Czech Republic, Denmark, Dominica, Dominican Republic, Ecuador, El Salvador, Estonia, Fiji, Finland, France, Georgia, Germany, Greece, Grenada, Honduras, Hungary, Iceland, India, Ireland, Israel, Italy, Japan, Kazakhstan, Korea (Republic of Korea), Kyrgyzstan, Latvia, Lesotho, Liberia, Liechtenstein, Lithuania, Luxembourg, Malawi, Malta, Marshall Islands, Mauritius, Mexico, Monaco, Mongolia, Montenegro, Namibia, Netherlands, New Zealand, Nicaragua, Niue, Norway, Oman, Panama, Paraguay, Peru, Portugal, Republic of Moldova, Romania, Russian Federation, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, Samoa, San Marino, Sao Tome and Principe, Serbia, Seychelles, Slovakia, Slovenia, South Africa, Spain, Suriname, Swaziland, Sweden, Switzerland, Tajikistan, the former Yugoslav Republic of Macedonia, Tonga, Trinidad and Tobago, Turkey, Ukraine, United Kingdom, United States of America, Uruguay, Uzbekistan, Vanuatu, Venezuela.
The list of countries – parties to the Hague Convention and the list of institutions authorised to issue the Apostille is available here: Apostille — Competent Authorieties by country.