The building can accommodate 780 pupils, with a wide range of modern facilities for students and the community.
Facilities at the new school include 3G sports and 2G hockey pitches as well as grass playing fields, a 100-metre sprint track, long jump pit and netball court.
An eco-garden pond is included alongside space for an orchard, allotment, outdoor classroom and an arts and craft garden.
A new library and gym is also part of the facilities on offer.
Councillor Carol Hamilton, Scottish Borders Council’s Executive Member for Children and Young People:
“The new high school will transform education in Kelso and will provide much improved facilities not only for pupils but importantly for the whole community.
“The previous high school had served the town well since 1939 but there is no doubt the new facility will provide additional benefits.