Keep it real
A This is not usually necessary or helpful. Children can usually be relied upon to be remarkably sensitive to children with more complex special needs (indeed, it is often those with mild difficulties who are more likely to be teased).
I suggest that you set in place the same welcoming procedure that you would provide any new entrant (for example, a buddy system), and try to treat the youngster, as far as possible, no differently from anyone else. This will send out an important message to your class, as children can sometimes "mother" children with Down syndrome and treat them as if they were much younger. Keep an eye out for this and prevent such behaviour taking hold.
* Please email questions to SNExtra@tes.co.uk or write to TES Extra for Special Needs, Admiral House, 66-68 East Smithfield, London ElW lBX.
Neither writer can enter into correspondence with readers.