Just 43 percent of students who entered their senior year in 2008 received diplomas last weekend, when schools closed their doors for summer vacation. The rest either dropped out over the past 10 months or failed their courses.

For many high school seniors, the biggest obstacle was the bachillerato, a series of nine exams. Some 36 percent of students who took the bachillerato this year failed one or more exam, up from 33 percent last year.

The hardest tests were math and physics, each failed by more than 20 percent of test takers. The easiest were Spanish, French and civic education, which were failed by just 6 or 7 percent of test takers. Students can retake the tests early next year.