Why is important for Students to Learn Art Vocabulary in the first place?

Knowledge of Art Vocabulary is essential for people to be able to talk about and interpret artwork at a deeper level. Having a specific vocabulary for discussing Artwork gives people a common ground for communicating. It is important for all students to learn this language in order for them to participate in the greater art world, as well as classroom discussions. When people know art language they can use that language to better identify aspects of their own work that are successful or problematic. This helps students grow as artists.

Another reason to teach vocabulary is that many of Califorinia's Board of Education Visual Arts Content Standards require that students know art vocabulary in order for them to meet the standard. (Specifically 1.0 Artistic Perception standards.)
Lets look at the first one as an example:
1.1 Identify and use the principles of design to discuss, analyze, and write about visual aspects in the environment and in works of art, including their own.
For Students to meet this standard Students need to know:

• what the elements and principles are (the vocabulary)
  
• how they relate to each other
  
• how to recognize them in various artwork