OK a serious answer. Just some things that may or may not help, perhaps you have tought of them or carried them out already

Does the child cry because it is leaving family and entering a strange environment where it is insecure and unsafe? Would working with the parent to gradually wean them away help? eg bring the parent in, let the child settle to an activity and thn the parent gradually cuts down the time spent in the classroom.

Is the child frightened because of bad experiences in the recent or distant past eg bullying from peers? Or from staff who are threatening in posture or volume? When greeting the child get down to their level so that you are not some huge big voiced stranger, even if it means going on your knees to greet it. Sit down, look relaxed and friendly. Obtain discipline and control by not shouting, use kindness and positive responses instead of negative and punitve ones.

Is there a language barrier? Is it possible to learn some words of greeting in mother tongue? have some familiar words or symbols around that relate to cultural heritage. (depends on reading ability) Have a toy , activity or something to distract the child. Meet the child in the corridor with a big smile, get low and offer an outstretched hand at their level.

These are some sugestions-I have more if you give more detail about the environment and class you are teaching, as well as more info about the child.

Does the child have special needs? Is there a possibility of some autistic tendency? How good is it's language base?

AliUK I have some 13+ kids who react the same way as 6 year olds! Think yourself lucky.

Spaceman get back to me.