Proofreading+Exercise

Please read the following sentences carefully and find out all the errors.

1) I am the only children of my parents. (x) 2) At home I help my mother to do the houseworks after I finish my homeworks. (x2) 3) At school I help my class teacher to clean the Teacher's desk and get some chalks from the General Office. (x1) 4) After school I play volleyball with my best friend Sally and Lily. (x1)