School is training. In that sense your teacher(s) are your boss, the principal the CEO. And yeah, in the real world I'd crack up if I heard someone tell the CEO to suck their dick. Hell, it's not only funny, but in reality that's for sure one less person in that corporation I'd ever have to compete with. Because in most situations that's going to get you royally fired on the spot, and hell, that's even funnier (well except to you). And those situtions where you might get away with it - like where I work - is also the kind of place where I get to turn around and reply: "Yeah, well when you really have one, instead of just being one, you can get back to me," and also get away with it. Or, lacking my fantastic sense of humor and wit, they'll just kick your ass. And no one will stop them because in Guyville, you just let your mouth write a check your ass can't cash. And, at either of those points, it might not be so funny anymore eh? Really, do you want to spend your transition money on restorative dentistry so you don't have eat through a straw? Nah.
But, back to a business/corporate/mainstream reality. Any guy - and you are claiming your maleness - who tells a girl/woman (the principal is a 'her') to 'suck their dick' is guilty of flat-out, open and shut sexual harassment.1 If she wanted to be a hard ass about it, she could not only kick you out of that school (leaving you to finish up in one of those 'special situations' were half the students drool on themselves and the other half have felony convictions), but file formal charges. Now, as you are 18, a legal adult and all that - then that sexual harassment suit (even if she does not win, which she will) will pretty much >-bleeped-< you up the ass without lubrication for the rest of your life, as most companies won't can not hire anyone like that, their insurance carriers insists upon it.
And I really try to avoid being the grammar/spelling police. But this is a very special situation. You are going to be in a position of authority. You are going to be setting an example. You will really be a role model. And how are you even going to correct their work if you don't know it yourself. Not a minor problem. Not to mention that some little wise-ass (like I was) is going to take great delight in loudly pointing it out to the entire class every time it happens. You felt humiliated with the principal, just wait till an entire class of porch-monkeys laughing AT YOU for not being as smart as they are! You going to tell them to suck your dick too?
But here's something else... When teachers sent >-bleeped-< home with my kids that had spelling/grammar or other critical errors on it, I went over and used it as an excuse to light-up the principal like the Fourth of July and take out all my frustrations with the educational system in a nice compact five minute tirade that included questioning their ability to do their job, to hire people smarter than the kids to teach them, and (as a tax payer too) what an incredible waste of my money it was to have hired this person, and even more of a waste of money to have hired them. And they had to sit there and take it, because there was not a single thing they could say because I was 100% right. There is absolutely no excuse for a teacher to send home an announcement or note with glaring errors in it. And after having chewed his/her ass down like a pencil in an electric sharpener, I'd go home feeling very smug and satisfied, and I'm sure he/she went out looking for that teacher like the Navy SEALS were looking for Osama bin Laden.
Now, this is also a situation where your principal is relying on the good graces of another principal to allow this kind of totally useless 'in school' training to occur. That other principal has certain standards (the lower you go grade wise, the harsher the rules - you know when I was in elementary school we could not eat or drink anything ever in class, but by high school we were allowed to have a can of soda, though still no food, and by college I could bring my whole lunch, a thermos of coffee and smoke in class too if I felt like it) for that school, and since you are guest, your going to be required to hold to them. Sure it retro-conservative, dumb, and all that. That's the way schools are. Schools are basically run on a compass that orientated to to cardinal points. One is the lowest common denominator group of students, as the school really can't go over their head, and they can't leave them behind. The other is the most narrow-minded, bigoted, and hateful, and usually highly religious, parents who must be appeased at all costs, least the school has to use all its money fighting lawsuits. And the other principal is just doing all he can to keep both of those groups in line. And your principal is trying to keep the other school happy or else no one else will get that 'experience' as part of their class in the future. It's really a no-win situation for your principal.
And, one more thing. Using i have mental issues as an excuse is really not helping your cause any. To me that would be one more reason not to allow you into that environment. And, as an adult, any excuses, all excuses are just lame. What you need to say for stuff like that is: "I am aware that I have a deficiency in that area, but I'm working hard to change that." Even if you don't mean it. Excuses are tools of the incompetent which create monuments of nothingness (in short, total bull>-bleeped-<), and no one - particularly other guys - want to hear them from adults. You'll always come off looking like much more of a man if you take responsibility, and if necessary, blame.
1. Also remember that every girl/woman is someones daughter, or sister, or wife, or girlfriend, or mother, and those guys might not find it as funny as Kentrie does. And though it's swell to have Kentrie thinking your all funny, he's not my first choice to back me up in a fight with a couple of brothers who resemble Coke machines with a heads who want to 'have a word with you' about what you said to their mom/sister.