Some children suffer from what used to be called overanxious disorder. This is now part of Generalized Anxiety Disorder, but the overanxious name is still a very apt description of the child who worries excessively about everything. Overanxious children often have bodily symptoms, particularly stomach aches and headaches. They may experience diarrhea or constipation, sleep poorly, have appetite problems, even worry themselves into low grade fevers. If a child has a lot of physical complaints but is not fearful, and does not worry unrealistically, she does NOT have an anxiety problem.
Malingering means deliberating avoiding work or school.
A child who invents a headache to get out of school is malingering. Probably most children do this occasionally. Very few children malinger more than occasionally. Those who do unquestionably suffer from some kind of serious emotional disorder and should be seen professionally. Calling a child lazy just puts a label on a problem that needs to be understood.