Well, how your parents see your use of cannabis really depends on what type of kid you are? Do you have any other hobbies that they do approve of? Are you doing well in school? If not, then it will be a lot harder, because you can't show that cannabis has not caused or at least contributed to your problems. If you are pretty well balanced and you are not a cause for concern for your parents, it will be a lot easier to convince them that minor cannabis use will not be an issue.