Mexico City, Mexico — Mexican officials say the first census of the country’s education system found at least a third of public schools have infrastructure problems and there are thousands of school workers who can’t be identified.

The census taken last year at public pre-schools, elementary, and middle schools said 41 percent of Mexico’s 207,682 schools have no sewage system and 31 percent have no potable water.

An education reform bill approved last year allowed the first survey of Mexico’s education system to be carried out. Until then, no one knew exactly how many schools, teachers or students exist in Mexico.

The survey found there are 978,118 public school teachers. Of those, 39,000 couldn’t be located. There are 21 million pre-school through middle school students in public school.