Why is this bird trying to get in my window?

there is a robin that tries to get into my kid's bedroom window it will sit on the edge or in the tree next to the window for hours and try to get in by flying up to the window and jumping up and down on the ledge. we had the same problem at the house we moved from 2 years ago but it was a cardinal and it would do the same thing at the kid's bedroom window. the two rooms are completly different and i cannot think of anything that would be attracting them i have tried covering the window but this does not work