You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Greece

Context:
Greece's post-compulsory secondary education consists of two school types: unified upper secondary schools (Γενικό Λύκειο, Genikό Lykeiό) and technical–vocational educational schools (Τεχνικά και Επαγγελματικά Εκπαιδευτήρια, "TEE"). Post-compulsory secondary education also includes vocational training institutes (Ινστιτούτα Επαγγελματικής Κατάρτισης, "IEK") which provide a formal but unclassified level of education. As they can accept both Gymnasio (lower secondary school) and Lykeio (upper secondary school) graduates, these institutes are not classified as offering a particular level of education.

Question:
What is one type of Greece's secondary education?

unified upper secondary schools