There sometimes is a reason behind his slowness...
He may be tired. I know I tend to move slowly before I get my first caffeine kick. Maybe he just needs to go to sleep earlier (with the summer coming around, it gets more difficult if bedtime is when the sun is still up). Or maybe even go to bed later; over sleeping may make him groggy and slow as well. Also you may consider giving him breakfast first (the food will give him some energy) and then go back to dress and get ready.
Or maybe there is something he doesn't look forward to at school. Bullies, a particular class he isn't doing well in or understand, a certain teacher that is too strict, missed assignments / projects (that was always my problem; I'd procrastinate on my book reports to the point that I didn't want to go to school and face the teacher getting on my case).
Or he may be distracted with something at home. I toy or game he wants to play with instead of getting ready. Even kids can get affected by WoW-syndrome where a particular game (or toy, or even a book) becomes almost like an addiction.
I'm assuming that he is young, but if he's hitting puberty then maybe he's getting interested in girls and is spending extra time trying to dress to impress. Similarly, even if it isn't that type of attraction they are dressing for, the kids may have a style / fashion going on in the school and he just wants to dress to fit in. I know one year after I got a buzz-cut I was much more wanting to get to school to show off my new hairdo since all the other boys were sporting buzz / crew cuts.
I've also heard that boys tend to be a little more lazier when around their mothers. If Mom constantly does stuff for their boy, the son will start waiting for mom to handle everything. Like the Momma's Boy that needs constant approval from mom in order to get anything done. I guess when I was young, I tended to be slower at putting puzzles together when mom was around than when she was absent (or when dad was there instead of mom).
The reverse might also be true if the kid doesn't feel like he gets enough attention from mom. Negative attention (like badgering him in the morning) is better than no attention. If the parents are over worked (with in this economy is always a possibility) or an addition to the family (a new sibling or new pet) may have the kid feel like he's not getting the same amount of attention.