Hi Elly,
What I have done in the past is just stop doing whatever it is I am doing whether it's lecturing or demonstrating a competency and basically stare at those who are disruptive. If that doesn' work, then I stop & ask, 'would you care to share your funny moment with the rest of the class. I have also asked them to leave the class & gain their composure in order to return. If all else fails & they refuse to leave class, then call the security guard to escort them out & write them up for unprofessional behavior.
