Islam stresses the importance of education as a religious duty.
There is nothing in Islam that forbids girls and boys are sharing the classrooms as long as they conform to the Islamic guidelines governing male-female interactions.
Men and women used to share public spaces including mosques and markets during the time of the Prophet (peace be upon him), and there was no concept of physical partition.
Islamic guidelines in this regard above all stress modesty and shunning of undue display of charm eliciting lustful stares and advances.
As long as these guidelines are observed, there is no reason to ban co-education.