" He that walketh with wise men shall be wise but a companion of fools shall be destroyed." 

--Proverbs 13:20--

What his is saying is that if you walk in with wise nice responsible people you will be wise and successful but if you are companion by a group of fools that aren't responsible and rude people then you will be destroyed and unsuccessful. Its saying that choose who you walk in with choose who's in your group and what group you want to be in because its going to represent who you are and the people in your group will also represent who you are and show what kind of person you are to those that are around you. If you choose a group or walk in a class or something with people that aren't responsible then that will make you look bad because seeing the other people i your group and seeing how that group acts then that will give people a wrong image of you and then the people around will think you aren't wise and responsible because of the people you walked in with.