You can think of it like how Luke and Anikan Skywalker are apprentices to Master Jedi Obi-Wan Kenobi. They learn from and work with Obi-Wan.
During an Apprentice Day we are inspired by a Master Artist.
During each art-time, every class has the opportunity to earn a color on the paint palette by demonstrating positive and constructive behavior. After earning all the colors, the class gets to experience an Artist Day because they follow the "Be Rules" (Be Prepared, Be Safe, Be Respectful).
On an Artist Day, students are able to choose what they want to create from a variety of special projects.