I understand your concern and would definitely address again but I do want to say it was the same when I was in school (in the 90s). Especially the bus. I heard all sorts of trash. My oldest did too. I had to give him a sort of age appropriate lesson on sex in kindergarten to correct the stuff he was hearing from other kids. It's really disheartening but I guess the silver lining is we've always had those open conversations with him and it has served him well into his teen years.
Oh wow! So young! I’m only 23 and I didn’t learn stuff till year 6 sex ed! I was so innocent my partner says 😂!. I would be the exact same I get playing mums & dads role play as a game what children do with dolls etc but kissing on the lips and things is abit much but it’s hard because they may hear their parents, see things, be affectionate anyway as kids are. I’d personally speak to the school again and discuss your concerns
Speak to school again and mention safeguarding x