Class at Mallaig School, about 1920?

Although many of the pupils in this photograph have been identified we are unsure of when it was taken. If you can help pinpoint the year we would be very grateful.

The people in this picture are:
Alex Aitchison (Eckie), Iain MacLennan, Willie Morrison, Bertie Maclean, James MacLellan, Donald MacDonald (Mallaigmor), Mr Lithgow (Headmaster), Bessie Wallace, Susie Mayne, Mary MacKellaig, Harriet/Lottie MacKenzie, Jean MacRae, Annie Downie, Ethel MacGillivray, Harriet Maclean, Peggy Mackay, Murdo Livingstone, Louis Crawford, Alex MacKellaig, ? Clarkson, unidentified