The hearing is routinely tested in all newborns in most European countries. Thereafter, no hearing test is performed in a systematic way, despite the many conditions that can cause hearing loss in the first years of life. If language acquisition is possible with only one ear, even a unilateral hearing loss can be the cause of learning difficulties at school. In Geneva, a screening program for hearing deficit was introduced in 1955 in all primary schools of the canton. This paper shows the efficiency of the program, which can detect unnoticed deafness, sometimes in children whose neonatal screening had proved normal. Such a program should be applied to all private schools and to schools for disabled children.