The top picture appeared in the Gazette of Friday 11 May 1951.  
As we learn from the caption, the 'May Queen' on that occasion was Kay Lewis:-

KAY (7) IS MAY QUEEN
Seven-year-old Kay Lewis was crowned May Queen at Breakspear School, Ickenham, on Tuesday.  Kathy Polak performed the ceremony, and attendants were from each class.  Kay was chosen from pupils in Group 5.

From the Gazette of the week before (Friday 4 May 1951) it would appear that there was a similar but separate event for the Infant classes.  The picture given in the Gazette has not yet been traced.  The text is as follows:-

BEVERLY IS QUEEN OF THE MAY
Newly-crowned May Queen Beverly Bennett (centre), with her Maids of Honour, Linda Latter and Carol Chaundler and two flower girls from the Infants class, at Breakspear School annex on Tuesday.  The ceremony, held for the third year, was originated by two teachers, Mrs. F. Nicholls and Mrs. Humphris, of Whitelands College, where a similar tradition was begun by John Ruskin.