Improper club selection is the number one reason most golfers are poor with their greenside shots.
When students want a chipping lesson, it is important to observe what clubs they actually use from different locations around the green. Most often one would find that various lofted wedges are the clubs of choice.
The oldest and most important rule of chipping is often either forgotten or ignored. I can remember as a young man my father repeating this rule over and over again.
"Minimum air time, maximum ground time". Put quite simply, this means get the ball on the green and get it rolling. Throwing the ball up high and landing it near the hole only increases the margin of error.