How much can my class rank change?

<p>Hello,</p>

<p>So at the end of junior year I got my class rank based off of the first 2 years of high school and 3 marking periods of junior year. Guidance reran the class rank and it is being released tomorrow and I am very scared that my rank dropped significantly from last year (top 6%). My grades stayed pretty consistent 4th marking period of last year, however, my grades for the first half of this marking period are very weak, but I don't think they can factor in 1st marking period of senior year since we arent even halfway into the marking period yet.
Basically my question is that is it possible that my class rank could have dropped significantly, even if I stayed consistent last marking period of junior year?</p>