What is the ruling on studying in mixed-gender universities?

Mixing in universities is one of the widespread evils, resulting from imitating non-Muslims and contradicting His —the Almighty’s— saying: "And abide in your houses and do not display yourselves as [was] the display of the former times of ignorance" and His —the Almighty’s— saying: "Tell the believing men to reduce [some] of their vision and guard their private parts. That is purer for them. Indeed, Allah is Acquainted with what they do. And tell the believing women to reduce [some] of their vision and guard their private parts." Studying in a mixed university is a great evil and a grave danger. It is not permissible except in cases of extreme necessity, and with reservation, seclusion, lowering the gaze, guarding one's chastity, minimizing evil, and choosing righteous companionship.