Is it deliberate that the boys are listed first (and in order) followed
by the girls?

Using your example and assuming data starts in row 2 with headers in
row 1, enter the following in X2 and copy down for the boys:

=N2 - RANK(W2,W$2:W$7,1)

and in X8 down for the girls:

=N8 - RANK(W8,W$8:W$14,1)

Adjust the ranges to suit your data. It would help the second part if
you had two cells somewhere which contained the number of boys and the
number of girls - assume Z1 (= boys) = 6 and Z2 (= girls) = 7. Then you
can put this formula in Y2 and copy down for boys:

=(Z$1-N2)/Z$1 (format as percentage), and for girls in Y8 downwards:

=(Z$2-N8)/Z$2, formatted as percentage.

Hope this helps,

Pete