Becoming a teacher with an expunged record?

I was arrested when I was 18 for possession of marijuana less than 20 grams. It was a misdemeanor and I completed a MIP program and had my record expunged. I recently applied for a teaching position and was honest on the application and was denied because of my charge. So I reapplied to a diffrent county in FL. On the new application I checked all the NO's on the criminal page. Is this something that they will find in their background check. My record has been expunged for over 5 years? Thx