People associate the term inappropriately, due to the correlation between graffiti and vandalism. If students are taught to respect others' property, then there is nothing inherently wrong with learning the art style.
And now to fill in the rest of the words needed. Seven more words to go. Two more.
School art classes should strive to expose students to as many different forms of art as possible. Graffiti has a rich history and cultural context that is a great addition to traditional art classes and it is a way to get students who are normally not interested in art to pay attention and get involved.
I think it's okay to teach art in the style of graffiti, but it should be called something different than graffiti. By definition, graffiti is art that vandalizes another person's property, or even public property. If this style of art is taught in schools, it should be emphasized that it is unethical to paint on another's property without permission.
No, graffiti should not be taught as a form of art because it usually is created in an illegal manner. Graffiti is almost always a form of vandalism against a piece of public or private property, and it is wrong to teach children that this is an acceptable form of art.
Graffiti is a form of street art. It is also generally illegal. Schools, therefore, should not promote it by teaching it in classrooms. Rather, it should remain a signature niche that is passed from one graffiti artist to the next. In treating graffiti in this way, it can continue to remain a street tradition.