I think the Shepherd is trying to teach them how to jump, and one of them looks like it came close to making it once

Looks more like a big dog trying to teach little dogs how to do it.

The shep turns and looks back, waiting for the little ones. It’s play, and the big one wants them to jump and chase too.

We had a tiny chihuahua cross (rescue, we don’t know exactly what she was) who would scale 1.5 meter tall wooden fences on our farm

No idea how she did it