I consider myself to be fairly smart and my grades were pretty mediocre in high school, simply because I rarely handed in homework or did projects unless I needed them to pass the course. I also never took notes, read any of the material or studied. In grade 12, I worked a little harder to get my grades up to the level that I needed to get into university. All in all, high school was a complete joke to me (as was university) and I didn't bother to go to my convocation or pick up my diploma at either as graduating really didn't feel like much of an accomplishment. The unfortunate part is that never having to work hard my whole life has set me on the path to failure in the real World as I get really discouraged and frustrated if I don't land a job right away. I have lots of motivation to work out every day and climb mountains but little for anything else in life.
On a side note, in my grade 11 social studies class, the teacher arranged the class so that the person with the best grade would sit next to the person with the lowest, the person with the second highest with the second lowest... etc. Apparently, I must have had the second lowest mark in the class at this time, so I was sitting next to a girl who was a straight-A student in all of her classes. Every time that we took an exam, and the teacher wasn't looking, she'd try and blatantly cheat off of me. Oh the irony...