Re: I (come home) or (come back home) from school at 3.00.
The only thing about both statements is that they are potentially ambiguous. Do you mean that you leave school at 3pm and then head home? Or do you mean that you arrive home from school at 3pm (therefore you must have left school before 3pm)?
If you're talking about your arrival time at home, you can avoid the ambiguity by saying "I get home from school at 3pm" (BrE).
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.