The boy isn't at school. - отрицательное
The boy is at school.
Is the boy at school? - общий вопрос
Is the boy or girl at school? - альтернативный вопрос
Is the boy at school or at home?- альтернативный вопрос
Where is the boy? - специальный вопрос
Who is at school? - вопрос к подлежащему
The boy is at school, isn't he? - разделительный вопрос