I always always always used to brush before, through the whole of school (and it followed on to my time at uni) because it was part of the getting up process and then I'd go downstairs and not have to go back upstairs again. Since being told I have to have a load of fillings and also since I moved into a single-level flat, I'm a lot less hesitant to just brush after.
Saying that, I did eat a cookie in bed after brushing my teeth last night. I felt guilty though.