You mean a cosmetology license. I dated a college instructor, there’s more one needs to know than most would guess. Long story short, there’s a lot of chemistry and health training. It’s shockingly easy to fuck someone up.
One example she gave me, “You can’t use $chemical on old people if their hands look like (whatever I forgot). That’s a symptom of (whatever) and their fingernails will fall off.” Heysus!
Or, “You can’t mix this and that. Makes a wildly exothermic reaction.”
And there’s no grouping “police” in America. According to the FBI, there are 18,000 police departments. They range from LAPD gang bangers to Mayberry cops.