look over one's shoulder
glance over one's shoulder

I glanced over his shoulder and had a look at the children.

He glanced over his shoulder to make sure no one else was close enough to hear.

He glanced once over his shoulder, then turned away again.

Her blue eyes turned away when he glanced back over his shoulder.

Then he glanced over his shoulder to see how the others were doing.

She started to speak, looked lost, glanced back over her shoulder.

With a start the child glanced quickly up over her shoulder.

She moved a little to the side and glanced over her shoulder.

Then he glanced back over his shoulder at the girl.

She went to the door, then glanced over her shoulder at him.