the entirety of the show takes place in school and it deals with the unpopular male mc being in love with the popular girl female lead. Maybe there's a love triangle between him, the female lead, and a popular guy. The unpopular guy and popular girl end up together in the end.
I see so many male characters being the popular school student and usually female lead is dowdy and poor. You might like the film Our Times, male lead is more of a thug but his reputation is well known. Female lead is not popular though, she's geeky and gets a makeover further in.
There is also historical school setting, SungKyunKwan Scandal which is awesome romcom. gender bender with female lead in disguise as a guy, she becomes slightly popular/well known while male lead is not very popular. There is also a forced living situation, and an almost love triangle.
Yeah, you see the "unpopular guy/popular girl" much more in anime/manga. In these live dramas, it's usually the other way around. I've seen like 1 or 2 where it's a rich girl/not rich guy, but usually that when they are adults. Well if you come across anything, let me know.
campus confidential = taiwanese film male lead is geeky and unpopular and the girl is popular takes place at a college (warning : expect a twist) some people like a surprise some people dont but if you do then i suggest you try it :) this was probably the only drama or film that i could think of that met the criteria cuz like you mentioned before, everything is unpopular girl likes popular guy
I don't know a drama with unpopular boy/ papular girl relationship, but for the opposite (popular boy - unpopular girl) here are some (Japanese/Chinese) dramas: Good Morning Call Love in Tokyo Master Devil Don't Kiss Me Operation Love (though here. they are BOTH popular) Best Get Going(though it's about interns and post college life) Suddenly Seventeen
For more "serious"/Melodrama dramas: Back In Time Fifteen years to wait for migratory birds
We have a hard time to find something like that in dramaland. Particularly korean. But you can check for
Adolescene Medley (Special): this is closest what you looking for one day (Thai movie and its not school): the guy is a mere, and girl quite popular Bring Itu On, Ghost!: Campus setting hello schoolgirl My Rainy days positive phisyque minami-kun No koibiito season 3