The movie How High stars rappers Method Man and Red Man. Their characters are named Silas and Jamal and their favorite hobby is smoking pot. When their friend Ivory dies they use his ashes as fertilizer to grow a new batch of pot plants. They smoke some of this stuff before taking the exams to get into college. This stash summons the ghost of Ivory who helps them get perfect scores on their tests. Both apply to Harvard and get accepted.
Once they get to Harvard they are told they need to keep a 2.0 grade point average to remain in the school. They pass all their tests with great grades thanks to the help of Ivory and their special stash. During this time they are also pranking the dean and stealing from the school. While they are out causing trouble at a school Halloween party their stash of special pot is stolen and smoked. They now have no access to Ivory or the extra help with their assignments.
Without their help they are having trouble in class. They try to study but still fail their midterms. Jamal suggest they dig up a smart dead guy and try to smoke his ashes. This plan does not work either. The person who stole the pot see Ivory during his high and return the plan but there is nothing left of it. The pair works on a truth serum that will save their grades but it continue to fail. Finally they get their serum to work as a last resort at a party hosted by the alumni. They used to very last of the plants with Ivory's remains to make the serum work. At first they are unwanted guest at the party only there on the invitation of an alumni's; daughter. At the party Ben Franklin's artifacts were going to be presented for the first time. As it turn out an important artifact from Ben Franklin was a bong. Salas and Jamal are able to present their serum and show that it really works. They wind up being allowed to stay at Harvard and even are able to get the girls of the guy who doubted them to date them instead. They continue to smoke pot as well.