First and foremost-- you must change your own belief. If you believe you need school to convince someone you can direct, then that's exactly the vibe they're getting from you. If you feel unsure of your ability to direct, educate yourself without school; get mentors, do set visits, read books, take courses, practice with a group of actors.
Technology makes it easy to direct a piece. The challenge is finding a good piece of writing to direct.
For more tips and articles by top entertainment industry coach, the Greenlight Coach, visit www.theGreenlightCoachBlog.com