The suicides themselves (not so much Cecilia's, although maybe depression ran in the family), made sense, but much of the plot was forced into a "It's a movie" - only, sense.

Why did Trip just leave Lux after banging her on the football field? (I know, "It's a movie," and the angst had to be created somehow.)

Why did the girls have the boys come over at midnight, the suicides would have been discovered anyway by morning?

In all, another Not Quite There movie from Sofia Coppola.