Most districts award higher grade points for Honors or Pre-AP classes. Harder course = higher grade points.
And with certain pre-AP and AP classes you can test out and get college credits.
My cousin was in the top 20 for the first half of his senior year. He became ill at right before the Christmas break. Because he was in Texas Childrens for about six weeks, the district required him to withdrawl from Cy-Fair and enroll in HISD(blech). They said he was no longer living in the district. It knocked him way down in rankings. However, he tested out of many college classes and started Texas Tech the next fall as a sophomore.