There are wrong convictions about the amount of sleep that children need and it is often considered that the adult 8-hours sleep range is applicable. Children need a lot more sleep, though needs vary according to age. Naps can be beneficial, but it is important to take into account the time at which they occur. A nap in the evening will delay nocturnal sleep: the child will fall asleep later and therefore sleep less, which will result in greater difficulty in getting up in the morning. It is a vicious circle. Children with chronic sleep deprivation have greater difficulties in abstract thinking – which is used, for instance, in mathematics – and may even have worse school performance.