In middle school and high school, it was practically a fashion statement to use four-letter words all the time. I suppose we used those words to act older or tougher, but in the end, it only made us look like fools.
Even so, it irritates me when there is deliberately-avoided profanity in YA books. I can’t remember which book I read, but in place of the f-word was “frickin” and it drove me crazy. It didn’t feel real to me. Teenagers curse a lot in real life. I couldn’t go down the halls of my high school without hearing the f-word pinging off the lockers like a stray bullet.
I’m not saying to use four-letter words a lot; just enough to remind the reader that, yes – this is a book that features realistic teenagers speaking in a realistic way. I recently finished Fall for Anything by Courtney Summers and I thought that book had a little bit too much of the f-word. But it was very realistic.
The moral of the story is… in YA novels, there is a delicate balance between too much cursing and too little. Some readers will be offended by just one curse word. But no matter what you write, you will offend somebody, somewhere. You can’t please them all, so do what feels natural for your novel and your characters.