All the teachers are also ESPers so as to maintain order.
After The Professor arc and the chaos that had ensued because of the unleashed ESP powers, there was a huge backlash on society and all ESPers had to be registered with the authorities. Every ESPer were given a metal bracelet that contained a monitoring device to help in peacekeeping. Because of societal stigma, ESPers could hardly lead a normal life and many had difficulties finding jobs or even enroll in school, with the bracelet as an obvious sign that one was an ESPer.
Efforts to improve the conditions of ESPers were made, notably by the likes of Rinka Urushiba, and eventually lead to the establishment of the ESP academy, a college that expressly admits only ESPers.