What is the name of this movie?

It was a movie we watched a few years ago and I can’t for the life of me remember the name. It was about aliens who were on earth but looked like humans and this group of kids were being trained and whatnot and they had this headgear that would show them if another person was an alien but they ended up being tricked into killing normal humans because the military was taken over by the aliens but again, they looked like humans. And I want to say some girl befriended some alien guy who basically defected to their side. It was a real neat movie but it ended so ubruptley and to my knowledge they never made a sequel. Very vague I know but thanks in advance!