What the heck was the name of this movie?

So this has been bugging me that I can't think of the name of this movie. It came out within the last 3 years or so. Its a bout a man, who may be a teacher not sure. and he has a son. There are aliens that come to the son but they do not hurt him. He meets a woman who has a daughter the age of the son. He purposely runs into her because of something of her mom. There is a significance of these black pebbles. At the end, He lets the son go with the aliens. Does anyone know what movie I'm talking about?