Air conditioning any building as large as most schools becomes an enormous drain on the electric grid. Air conditioning demands trigger brown-outs in major metropolitan areas during the summer because air conditioning taxes the electric grid. Since few schools rely on solar or wind power for energy sources, school systems need to consider the size of their carbon footprints and how they consume finite environmental resources. Energy consumption also translates to pollution in the hazy summer skies around most urban areas.
All schools, public or private, from huge universities to small neighborhood elementary schools, must monitor expenditures closely, especially when state and federal governments operate with deficits. If schools have to cut back on something, air conditioning seems more reasonable than textbooks, teachers' salaries or classroom supplies, especially when we know that schools can educate students without air conditioning.
Few schools operate year-round to justify the costs of air conditioning. Air conditioning may seem like an extravagance for schools barely operational during the warmest months. May and June seldom get that hot in most locales to become unbearable for students and school personnel before the school year ends. Indeed many schools send students home ---sometimes on un-air conditioned school buses to un-air conditioned homes --- when the temperature reaches the 90s, regardless whether the school's air conditioning functions well or not. After June, most school systems air condition buildings for a skeletal staff. If the school provides summer school classes and camps, they often don't take up the entire day, and hence air conditioning the building becomes financially and ecologically wasteful.
Air conditioning systems need constant maintenance, and often they seem to break down on hot days when needed most. Calling air conditioning repairmen becomes another expense along with maintenance contracts for school systems that are already often debt-ridden.