The levels are a template or guide, not a competition. They are made up of developmental goals and a way of moving rather than exactly what exercises you do.
The levels are most obvious in a mat class as in private sessions the work is customized to you.
Basic Beginners, no matter how fit, need to attend Basic Mat classes. These classes teach you the basics of the method through a series of simple, challenging exercises. The goal for this level is to find your “power house”, to begin to find “lift” in the body and to even out the alignment of the torso. You will start to feel the benefits of Pilates.
Intermediate When your body has absorbed the basics of Pilates you are ready to take intermediate level sessions. The aim of this level is to strengthen and deepen the power house. Some new movement patterns are introduced for the first time (e.g. back bends), and other patterns already present in the basic level are deepened
What makes you intermediate is not how long you have studied, but how much your body has absorbed.
Advanced At the advanced level the focus is on increasing the stamina of the power house. More upper body exercises are introduced with the aim of working the upper back and connecting it more deeply with the rest of the power house. The advanced level is where complete flow and synchronization with the breath take place.
There is nothing to be gained by trying to rush ahead in your progress. Impatience means that you will simply not get as much from your classes as you could. If you have an injury or illness it is advisable to have private sessions first before you join a mat class to ensure your needs are properly addressed.