is this sentence right ? as mr. john said, we must go to school earlier than the student.

You should rather say: As suggested by Mr. John, we must reach the school before students get there.
(Also a good practice in English is to use the surname after Mr. in formal settings. So if John's surname is say Williams, then you should say Mr. Williams instead of Mr. John)

sentence is right but grammatical mistake was "quotation marks "