If it's for kindergarten, I would say morning circle or morning gathering. If it's at the workplace, I would say morning meeting.

It is called circle time.
My daughters teacher would say things like:
She really likes circle time.
We sang a new song at circle time.
This picture is from circle time.

It is called circle time. At least this is what my daughter 's day care uses in Texas US. However their circle time can also be.