This intervention will aim to raise the awareness of the importance of having a good quality sleep at night and to teach healthy sleep behaviours that will contribute to improving sleep hygiene. As a part of this intervention, eight activities will be carried out at home and at school. During the first activity, parents and children will attend a general talk about sleep and health and will sign a contract for a "healthy sleep at home". Signing "the contract" will enable participants to have an active role in the sleep intervention. Also, with help of their parents at home, children will complete a diary in which they will keep a record of their activities prior to going to bed and after waking up in the morning. The objective of this activity is to strengthen the importance of a routine before going to sleep and its benefits on the adequate sleep behaviour. Parents will be given a manual to help children use an adequate sleep routine and reinforce children's achievements. At school, several teachers assisted by the researchers will implement the activities. The first classroom-based activity will be based on the educational program "I have a dream" (Spanish adaptation of the SimplyHealthy@Schools International Program; Philips Ibérica, S.A., Madrid, Spain). The remaining classroom-based activities will include with a group art project with questions and answers about sleep, children's calculation of their own sleep parameters from the sleep log data, and discussion groups about the sleep diary completed at home and other sleep issues, as well as strategies to achieve the commitments included in the "signed contract". In addition, the class teacher will introduce the concept of relaxation and its benefits at bedtime and will teach an abbreviated version of the Jacobson's progressive relaxation technique every morning after the recess.