Signs in Spanish at DISD

A FrontBurnervian corrects my earlier post by noting:

All DISD signs have messages on one side in English and the OTHER side in Spanish. This photo was in Pegasus, and is only (literally) one side of the story. Lo prometo.

But why use Spanish at all? Shouldn’t middle-school students, at the minimum, know enough English to read a simple announcement of when school is starting? Couldn’t we challenge them a tiny little bit?