This Needle Finger Guard is a good thing to have when teaching your young ones to sew.  Acts as a visual aid for them to learn the area for which to keep their fingers away from. 
 
Be sure to study the photo carefully to know which direction it is attached.  It took a little fiddling to figure it out, so hopefully the image above will help.  Attach your presser foot as you normally would without tightening the screw all the way -- loop the curled end of the guard up and from the back around the threads of the screw as shown in the photo.  There is also a u-shaped side which is designed for clearance so that you can continue to access and thread the eye of the needle.