Headaches caused by stress and tension are not especially unusual for young children but are somewhat more common in teens. Nonetheless, when your child has a headache, it is most likely caused by a minor illness, allergies, undiagnosed vision problems, or getting too hot or tired. If your child has a headache more than once a month or so, it needs assessed by a physician. If the headache is severe or is accompanied by vomiting, check with a physician immediately. Rule out possible medical causes before considering stress as a likely cause of your child's headaches.