"I am going to school by bus everyday" is grammatically not correct.
"Present continuous/progressive tense is used to talk about temporary actions and situations that are going on 'around now':before, during and after the moment of speaking. We often use simple present tense to talk about permanent situations, or about things that happen regularly, repeatedly or all the time".(Practical English Usage-by Michael Swan)
Simple Present Tense is used in general statements of what was true in past time, is true now, and is likely to be true in future time-all-inclusive time.
I go to school everyday by bus. means: bus is my means of conveyance to go to school(yesterday, today, and tomorrow).
How does he earn his living? - He sells books. The Simple Present Tense verb sells means that he sold books yesterday, he is selling books now, and he will sell books in the future.