If you think you lack the experience for the position then you're not going to get it. That's not the mindset you want to be going into an interview with. Just because you're out of school and not going to College doesn't mean you lack the education to be a software developer.
Have you got any experience in the languages you are applying for or are you applying for entry level positions that don't expect you to know the language? This question makes a difference. If they don't expect you to know the language, then education isn't a massive factor in terms of the language. Your school grades will count but what will count more is how you think, do you have a logical approach to solutions, do you know any similar language? That's more important in a prospective entry level position where they are going to teach you. You need to show that you are receptive, eager to learn and most importantly, capable of learning.
If you're going for a position where you are expected to know the language, again you don't have to have a college degree, but you will have to demonstrate command of the language. Do you have code samples you can show them? Build a portfolio, even a small one, of sample programs and code you've written. Have you worked on open source initiatives? Great, show them you've contributed; this is all experience.
Not everything has to be about your school work for a school leaver.