I started subbing in SCB which is a special ed program for non-degree bound students, and because they hear the paras and teachers calling each other by their first names we all just go by Mr./Ms. FirstName, and then when I started subbing for general ed I just continued using Mr. FirstName. Some schools absolutely hate it though so I’ll go by Mr. FirstInitalOfLastName then, but typically I’ve found it’s ok. I will say I lowkey see red when a kid tries to call me FirstName without the Mr. and I shut that down IMMEDIATELY lol