Well this is something you're going to have to face....he is right, you don't NEED to go to college to mow lawns and ANYONE can do it. You have to make a name for yourself and set yourself apart from others. But if you stay a mow only guy people will always thing that. Going to college will help though! And the way you carry yourself, shows a lot about what you think of what you do.
bottom line is though, anyone can do it (this site proves it, i.e. some of the members). I mean even you prove it, you have one 36" mower and a bunch of 21" mowers and are 15. What other legit business could you possibly own at the age of 15??? Or even at my age of 18???