Many students dedicated to becoming artists in their own right will often take many art classes in different categories before they graduate, but some of them will still choose to learn more. The classroom is not always the ideal place for them to learn what they want, so some of them will choose to sign up for an apprenticeship with an artist already working in their field of study. Many of these positions pay nothing, and some artists will charge a fee for students. This might seem prohibitive, but many art students feel the knowledge they will gain is worth any price.
There have always been trades where apprenticeships were the way to gain insights into a career, and artists have been an important part of this process. They do not lecture at the front of a classroom because words will not convey what they are trying to teach. Instead of teaching in the oral tradition of many subjects, they use visual techniques. This is what separates them from many of the classes that students use to learn their subject matter.
Each form of art has its own techniques a student must master before they can feel confident enough to make their own creations, and artists have passed this knowledge down to apprentices for centuries. Teaching a student how to add color to glass is done in the workshop rather than the school room, and the training is a way to reinforce the information. Artists count on this to transfer advanced knowledge of their subject to newcomers.
Not all art students will choose to serve apprenticeships, but those who do are generally determined to have a successful career in their chosen field. They learn from masters the minute details that will help them find their own place in the world of art that they could never learn within a classroom.