FOR PEOPLE WHO KNOW ABOUT 'THAT 70S SHOW':why do they go to a prom in season 1 when they aren't even graduating high school that year?Please someone tell me. Thanks :)

In the 70's they just had a prom. If آپ were a Senior it was your Senior Prom, if آپ were a Junior it was your Jr. Prom, etc. They would have gone to prom every سال they were in HS.