Helping Kids Use Islamic Expressions Respectfully

Salaam, I'm an educator in a school with many Muslim students. Lately, I've noticed students, both Muslim and non-Muslim, using 'wallahi' in casual chats to show they're being truthful, kind of like saying 'I swear' or 'on God.' They're mostly the older elementary kids. From what I've learned, 'wallahi' is a serious term in Islam, meaning 'by Allah,' and using it lightly can be disrespectful. I initially thought it was harmless and didn't want to step in since it's not my background, but I don't want anyone to get hurt or offend anyone's faith. If it's considered offensive, what's a gentle way to address this if I hear it again? I'm trying to be mindful without overstepping. Any advice from those who know better would be appreciated, jazakAllah khair!