We have a row of pyracantha bushes at the bottom of our garden. You can train them up a fence. Get two or three bushes with different colour berries and you get a great display in Autumn. It's also great for wildlife.
Hawthorn is similar but makes a better bush/hedge, i.e. you don't need the fence to train it up.
If she fixes the fence, she will have more choice of bushes. If she grows something thorny and it grows through or over the fence onto the school area and a child gets injured, she could be responsible.