Hello Ted. I do commend you for the motivation and ability to give marketing advice at such a young age. If it's working for you, I'd keep at it.
However I still recommend finishing high school and college before beginning this business full-time. There is much competition out there among marketing firms - to have a chance at standing out among them you need to have the basic 'requirements' in-place, which almost always include at least a bachelor's degree. Whether a bachelor's actually makes you a better marketer is up for debate, however it's a basic requirement that clients look for.
Additionally, experience is another important aspect for clients. To scale your business, you'll need larger clients which means more experience. Catch 22, right? Well to get this experience you need to continue working for smaller companies, and even find yourself an internship at a marketing company.
With hard work you have a great chance to become successful - just remember to play it smart as well.
10+ years investment experience; corporate finance/accounting/auditing experience; author of "The Stock Market Outsider: Becoming a Billionaire"