TIFU by sounding like I was offering a NSFW service to a classmate

This is historical, and mortified me at the time, but thought I would share as time and distance have removed the sting.

Background context: at this point in my life I (F, 16 at the time) was very Christian, and never got into physical altercations. The classroom size was around 30, of which about 25 were boys.

In one of the mistakes of my life, I took physics in year 12. The teacher wasn't good at teaching the subject, but the sole benefit of the class is that it tended to finish early. Waiting for the bell, we would tend to stand around with our friends, in different areas of the classroom, chit-chatting. As you can imagine, the classroom would be quite loud with 30-odd teenagers talking to each other.

For some reason that made sense at the time, I was pretend punching my male (16) friend on the upper arm. He leaned into the joke, and started leaning away, going "oof, ow" and other comments like that. To which, and I remember it to this day, I said " that's not hard, do you want to feel hard".

Immediately before that sentence, the whole room had gone quiet in anticipation of the bell. I had spoken those words at the volume you would expect in a noisy room. All eyes were on me, including the teacher's.

tl;dr: words I used innocently in a classroom were heard by the entire classroom, out of context, and it sounded like I was offering to perform NSFW activities for a friend.