How 'bout taking the honest route...
"Im really not that good in the sciences. I mean, I try, but I always seem to not be able to grasp certain concepts that are critical to the course. Thats always been the case with me and school. Even with 3rd grade social studies when we discussed the different foods the Cherokee Indians ate. Basically, if it requires brains or requires memorization, count me out."
"Also, I tend to leave schoolwork for the last second. I get distracted really easily, like if Real World is on or something, I tend to stop my work and watch it. Then, I get sucked into Sportscenter after that. Before you know it, its 1:30 am and Im watching Howard Stern. Usually when this happens, I just decide to think of it as a lost cause and start a new day tomorrow."
"Lastly, Im not really a people person. Being the only child and hating school, I never really developed the skills necessary to form relationships with others. Therefore I was a loner while at school and a loner at home, since there were no other kids in my family to play with. So, after 24 years, Im just used to being on my own and I basically despise being around others. Working in groups is probably my least favorite thing to do."
"With all this said, I think I am a good candidate for dental school."
*and just because I have become somewhat paranoid all of a sudden, if any adcoms are reading this, its just a joke. Im really a good student. 😀 I even have 3 sisters, so that part involving being the only child was developed to enhance the quality, or lack thereof, of my story.
EDIT - I just saw Iceman's post, he beat me to the punch. Damn.