I have two small maybe 2.5inch x 1inch ones, one on the top of my forearms, just below the elbow crease, they are black letters, chemical formulas to be exact, easily covered (I also have pieces on my upper arms, including a half sleeve piece but it would have to be covered anyways to cover the smaller lower one)
The big one though is I have a full chest piece, it extends somewhat high but not up onto my neck or anything, I'd just need a higher neckline or a tshirt under neath. I also have no issue wearing longer sleeves in the warmer months either, I'm going to school to be a 3rd grade teacher! I have no problems with ironically having to dress more conservatively than my peers.