A 16 year old boy does not attend school because of the fear of being harmed by school mates. He thinks that his classmates laugh at him and talk about him. He is even scared of going out of the market. He is most likely suffering from:
The history is suggestive of delusion of persecution (fear that schoolmates may "harm" him) and delusion of reference (belief that classmates laugh at him and talk about him). Had they not used the term "harm" and "scared" a diagnosis of social anxiety disorder could have been enteained.
Anxiety disorder
Manic depressive psychosis (bipolar disorder)
Adjustment reaction
Schizophrenia
Schizophrenia Spectrum and Other Psychotic Disorders