We are prone to concentrate on the technical elements of playing and do not often get to the musicality or even the aural phenomenon (what we hear). That allows our students to be concerned with only the mental and physical parts of playing.
We think that they certainly hear the music, but that is an error on our part. Encourage them to hear the music before they play it - which means you have to start with something simple like unison concert F.
Until they become aware of their responsibility in hearing and analyzing results, they are not in your musical world.
How do you develop kids' ears so that they hear and fix mistakes?
I have kids missing key signatures all over the place. Mostly inner voices, so that's a little tougher, but even playing scales. They don't realize they're playing a half step off from everyone around them.