Actually, Theodosius closed every school considered Pagan(Greek too), and imposed Christianity as the only religion in Byzantium. He is mainly responsible for the end of ancient Greek civilization. I'm not sure though Egyptians were Muslim when this happened.
Theodosius did not close down any school, he closed down the temples. Schools were separate institutions and were untouched.
Some [polemicists] conjure that the temples also functioned as schools, and hence they say he closed down schools, however that is not the case, it is purely imaginative misinformation hanging around for meme's sake due to its populist anti-christian overtones. Temples were not schools but banks, and the curriculum of schools inside Rome's borders was thoroughly Pagan, during Theodosius and afterwards, even inside exclusively christian schools. After all the christians hated Julian precisely because he banned them from teaching Greek classics and as such from being able to teach anything all-together. "Persecution" of christians consisted of making them unable to teach pagan literature, and their curse was to "stick to Matthew and Luke" instead. The irony of this sentence never fails to amuse me.
Anyhow, Theodosius not only did not close down schools and "forced Dark Ages" as Zyx quoted, but founded Universities such as the University of Constantinople
, which was the first university in the planet devoted exclusively to secular(aka "pagan" in the lingo of the times) studies.
"The Dark Ages"
At the time various economic schools, colleges, polytechnics, libraries and fine arts academies were also open in the city, making Constantinople the spiritual centre of the medieval world. Byzantine society was educated by the standards of its time with high levels of literacy comparative to the rest of the world. Significantly it possessed a secular education system that was a continuation of the academies of classical antiquity. Primary education was widely available, even at village level and uniquely in that society for both sexes. It was in this context that the secular University of Constantinople can be understood. Further it was not unique in the empire as for many centuries, before the Muslim conquest, similar institutions operated in such major provincial as Antioch and Alexandria. 
The original school was founded in 425 by Emperor Theodosius II with 31 chairs for Law, Philosophy, Medicine, Arithmetic, Geometry, Astronomy, Music, Rhetoric and other subjects, 15 to Latin and 16 to Greek. The university existed until the 15th century.
The main content of higher education for most students was rhetoric, philosophy and law with the aim of producing competent, and learned personnel to staff the bureaucratic postings of state and church. In this sense the University was the secular equivalent of the Theological Schools. The university maintained an active philosophical tradition of Platonism and Aristotelism, with the former being the longest unbroken Platonic school, running for close to two millennia until the 15th century 
EN EL ED EM ON
...take your common sense with you, and leave your prejudices behind...