This was such a stupid storyline. All the kids went to prom together and Mel Silver had them over to his stupid bachelor condo beforehand and gave them champagne and then they had more champagne in the limo and because Donna was pure and virginal and had never even breathed air that had been exposed to alcohol before, she got good and wasted.
They tried to sneak her out but Ms. Teasely totally busted her all hiccupping and babbling and then told her that because of some new rule about zero tolerance Donna would not be allowed to graduate. And Donna may have been stupid and had some kind of unspecified learning disability but she totally wanted to graduate! No fair making her take responsibility for her actions! And for some unexplained reason Brandon got all excited about it (something about the process the school board had used to make the rule) and organized a walkout of HUNDREDS of students all chanting “DONNA MARTIN GRADUATES” and the school board was powerless against such a massive demonstration and caved and she DID graduate. And then never used her education ever again.