I don't let them into the classroom until they have individually answered a simple question.
An old favourite is to ask at random 'Who are you?' and 'How are you?' with similar intonation.
I have a related activity prepared and already running in the classroom for those that are successful and get to sit down.
This ensures a controlled entry into the class.
Sometimes I let one or more students be the door entry keeper. This is also expanded into an activity like a frontier control point with a sign, flags, desk and barrier. The corridor in my case being France and the classroom being England.
We continue this even further during the lesson with the threat of those who speak French in class without permission get 'deported' back to the corridor!