How is the Overall Champions banner decided?

It is based on team place finishes in the divisional races (girls and boys, all three divisions). Points per team place:

1st 20, 2nd 18, 3rd 16, 4th 14, 5th 12, 6th 10, 7th 9, 8th 8, 9th 7, 10th 6, 11th 5, 12th 4, 13th 3, 14th 2, 15th 1.

The school with the most points from all three divisions wins. Ties are broken in this order: (1) the school whose top scoring team finished closer to first; (2) the school whose second scoring team finished closer to first; (3) the lowest total of team scores from all races, not including the para race; (4) if still tied, both schools are awarded the championship.