Hey Mehrdad, 'Are you IN home' is definitely incorrect. 'Are you at home' is completely fine. However, I would say that we'd simply say 'Are you home?' With regards to the ESL point, yes, my first day at school is better. 'In school' has a slightly different connotation. 'Michael's still in school'. i.e. he is still a student and therefore studying at school. Hope this helps! Matt

Are you at home? is the correct sentence We use at with school/college/university or to refer to an address: He always did well at school. They once lived at number 10 John Street. We use in: to talk about locations within a larger area: I know my book is somewhere in this room. Can anyone see it? Please see https://dictionary.cambridge.org/grammar/british-grammar/at-on-and-in-place for examples.