"That is our high school."

Translation: 那是我们的高中。

[slalomrain]

为什么«那是我们高中 »不对吗？

[George792719]

Because sometimes they want a 的 to show possession of an object and other times they don't. They teach us that Chinese people often leave out the 的 but they never say when they expect it, and when they don't expect it. The course is simply plagued with inconsistencies and not enough answers, yet they never seem to do anything about it.