Thank you so much for the question, Amy Z.
This is a great question because it is a little tricky and there are many different opinions. 😉 When working at the barre your heels shouldn’t be lifting off the ground but you should be imaging that they are in order to create the feeling that your body weight is over the balls of your feet. We are training our bodies to have our weight NOT on our heels and therefore it can sometimes be seen as a exaggeration by lifting the heels off of the ground.
Imagine that you have only one piece of paper that could slide underneath your heel. That is how much your heel should be off of the ground. It really shouldn’t be visible.
If you pile with your heels coming completely off of the ground then the calf and leg muscles aren’t being used or strengthened in a way that will benefit you.
When you are dancing a variation, you still want to use your full pile with your heels on the ground but sometimes you will see the heels slightly lifted as the dancer is changing or prepping positions. This is normal. Especially when you are working with speed because that is when it is even more important to have your body weight on the balls of your feet. You can’t move quickly if your weight is positioned incorrectly.
Jumps. Well… technically it should come from a pile with your heels on the ground. Honestly, it is common to see dancers jumping from a visible but slightly lifted heel. It’s again about your body weight. Getting your weight in to your heels is death to a jump.
All fifth positions, all pile’s, and all preparations for jumps, if done correctly, should have the heel down but with the weight on the balls of your feet. That way your legs are ready for any step that comes your way! 🙂