Hey Nathanael,
Have you watched Bill Mollison's Global Gardener series?
The section on drylands he speaks about living fencing material, and the purpose of termites in the landscape.
This is where he talks about planting living fences.
https://youtu.be/P1HWOQg8-L4?t=552
This is where he talks about termites.
https://youtu.be/e9QssyxOfck?t=74
Turns out termites are really good at making compost piles, and growing trees. I don't know the range they have for collecting material, but it seems like a really cool addition to a permaculture setup.
Also, is that the type of termite that can be eaten?
Also, your pit garden seems to get a lot of moisture in the bottom. If you were able to get enough mulch down there do you think it could support a mango tree?
You mentioned they needed lots of water and it looks like the wettest place on school property.
Also, do you know of any local plants with dense fine roots to hold the soil?
If you plant that on the edges in the direction of the blowout in your retaining wall they should help hold the soil so you don't have to work as hard.
I don't know any specific plants there so I couldn't hazard a guess.
Hopefully this helps you find some of the answers you were looking for.
- Justin J.