THE Liceo Bicentenario San Pedro is a modern secondary school in Puente Alto, a gritty district of Santiago in Chile. Opened in 2012, the school nestles amid the vestiges of a shantytown where urban sprawl meets the vineyards of the Maipo valley. Most of its pupils are drawn from families classed as “vulnerable”. Yet in national tests it ranks fourth among municipal (ie, public) schools in Chile. The school has done well by hiring committed young teachers and by offering them more time for preparation and in-service training, according to Germán Codina, the mayor of Puente Alto. When Bello strolled around the liceo recently, he saw teachers who visibly commanded the attention of their pupils. Sadly, it is far more common in Latin American schools to see inattentive children talk among themselves while a teacher writes on the blackboard. It is schooling by rote, not reasoning. And it imposes an unacceptable handicap on Latin Americans.

The region has made big strides in educational enrolment. In 1960 the average adult in Latin America and the Caribbean had just 4.3 years of schooling; in 2010 that figure was 10.2, only a couple of years less than in developed countries. The problem is that Latin Americans don’t learn enough. The international test known as PISA shows that at 15 they are more than two years behind their peers in developed countries in maths and reading comprehension. It is the quality of learning, rather than mere attendance, that drives economic growth.

The main reason for Latin America’s educational failure is simple. The region churns out large numbers of teachers recruited from less-bright school leavers. It trains them badly and pays them peanuts (between 10% and 50% less than other professionals). So they teach badly.

That last point is made in a groundbreaking new study by the World Bank. In the largest-ever international exercise of its kind, the bank’s researchers made unannounced visits to 15,000 classrooms in more than 3,000 public schools (both primary and secondary) in several Latin American countries between 2009 and 2013. They found that the region’s teachers spent less than 65% of their time in class actually teaching, compared with a benchmark of good practice in schools in the United States of 85% (see chart). The rest of the time was spent on administration or simply wasted. That is the equivalent of more than one day’s schooling lost per week. The observers also found that despite abundant teaching materials and equipment (including laptops), teachers relied overwhelmingly on the blackboard.

Closing the gap in learning demands far-reaching changes in the way teachers are recruited, trained and rewarded. Reforming an entire profession is complex, especially since teachers’ unions tend to be powerful in Latin America. But some countries have made a start. A sine qua non is national testing of students and the publication of schools’ results.

The next step is to introduce in-service evaluation of teachers, and to link pay and promotion to performance instead of seniority. Half a dozen places, including Chile, Ecuador, Mexico, Peru and Rio de Janeiro, have passed or proposed laws to do this. But none has yet had the courage to implement a rigorous evaluation system under which teachers who fail are ejected from the profession.

In many countries, falling school rolls—a result of demographic change—provide a matchless opportunity to pay more to good teachers by weeding out the weakest ones. Reforming their career structure can also be the best way to attract brighter recruits to the profession, according to Barbara Bruns, the report’s lead author. She adds that school principals should be encouraging teachers to learn from their colleagues: the bank found big variations in teacher performance within schools as well as among them.

Not all is gloom. Chile, Peru and Brazil have all seen improvements in their PISA scores over the past decade. Nowadays education is at the top of the political agenda in the region. That is especially true in Chile. Influenced by a powerful student movement, its government is proposing an expensive reform to ban public subsidy of for-profit schools, parent co-financing and selection. It might get a bigger return by using the money to invest in world-class teachers.