I watched IT when I was thirteen and it didn't scare me horribly. It was pretty good, but parents should know it has a lot of blood without much intense violence, examples are blood coming out of popped balloons, a fortune cookie and blood in a tea glass falling on the floor. The violence isn't too bad, a spider gets killed and pennywise's face melts some, this isn't too gory. A character commits suicide by slashing his wrists, not onscreen but you do see bloody results. A violent bully comes close to cutting a fat kid's, well fat off his body but it doesn't happen. At the beginning,* SPOILER* Pennywise kills a young boy, it is offscreen and is suggested that he bites the kid's arm or eats him, its not 100% clear, interpret it anyway you like but he still dies. And another violent scene is where a man gets stabbed but he lives. Overall the violence isn't too bad, but it still has a lot of blood. Sexual stuff includes a scene that looks eathir after or before sex, no genitals, boobs etc. are shown. A man admits hes a virgin. Not too bad. A good amount of swearing in this film also, but no f-bombs. This movie is not for little kids, some will be quite scared of Pennywise the clown. Tweens should skip this one too, but 14+ teens should be okay.
What other families should know
Too much violence
Too much swearing