How closely does adcom look at school profile

I know that grades and rigor or classes are important to adcom. From what I gather, they look at the school profile to get an idea of the strength of a transcript. How closely do they scrutinize each class? My school is a small competitive high school (graduating class of 150). The school profile is broken down by class title and by grades A+, A, A-, B+ etc. There is a required (writing) class that is taken by all seniors their first semester of senior year. I have a teacher that grades really tough and it looks like I am going to end up with a B which puts me in the bottom 10 percent of the class. My other grades are in the upper 50 percent of the profile.