Idk if you knew but I felt the need to mention this, so here I go. Nothing tears during sex, even for the first time, if done properly. Hymen is almost always perforated already, which is also why and how you get periods regularly. When the hymen is intact in very rare cases, it actually needs to be surgically cut for teens in order to let menstrual blood out or else it will pool up inside and cause problems.
Uhmm for the period fact, I don't think that is factual, I have my periods but I didn't have mine surgically cut when I was in my first period, and there is no such thing as pooling up since ours open up in menstrual period. And hymen is a very thin skin that tends to tear out if a sudden penetration happens, but since this is just fiction, it's passive for me, its just I got into the story to bring this up although I know the spoilers
I suggest you look it up if you doubt it, no problem. You didn't need to have it surgically cut just like the heavy majority of girls, because the hymen is indeed perforated for the majority (that's why I said almost always. search it up if you'd like). Hymen doesn't open up during the periods and doesn't go back to being closed or something like that afterwards. That is why, a small minority of girls whose hymens aren't perforated need to have it surgically cut open or else their menses indeed do pool up, which is obviously a problem.
I don't know what your biology teacher said but this is 100% a fact. I think it'll be a good idea for you to read more about it on your own :]]

God I was nervous for her, she is a virgin at heart and I thought her hymen would tear(but it did not??), because if it did he will know that she is lying??? (Though in the spoilers it isn't)
I felt that painful sensation down in my Virginia goodness