I’ll have to disagree with ya there, IB. Perhaps it may be true in some cases, but it’s too simplistic an explanation to cover all (or, i believe, the majority) of cases.
Take the Maori tattooing tradition (Ta Moko) which is an important cultural practice, and sacred form of family and personal identification. It’s integral to their very culture. In fact, many tribal cultures have tattooing, scarification, and other body art as part of their cultural practices and beliefs. I certainly wouldn’t pigeonhole them all as having unhappy states of mind en masse.
I would argue that your example of prison tattooing probably has much to do with the same social pressures of conformity, assimilation, and culture, more so than being a symptom of psychological problems. At least one study has been done to investigate the possible links between self esteem and tattooing, and found no statistically significant link between the two.
I myself have several tattoos, and I can state that I got none of them while depressed or in an unhappy state of mind, and that I felt no disdain for my body in doing so. In fact, I consider my tattoos a very personal form of permanent body art, and very much a part of who I am. I spent a long time (years, in fact) deciding on my first tattoo, being cognizant of the fact that the tattooing would be a permanent part of me.
Tattoos and other body art are much more socially accepted these days, at least where I live. I’ve seen bank tellers, school teachers, and HR managers with tattoos, nose rings, and eyebrow piercings. Where I work has a written tattoo policy that states only that “offensive” tattoos must be covered.
I see no problems with teachers having inoffensive tattoos, nor do I think that they should be forced to cover them.