The serapes and giant mustaches represent a mocking stereotype of Mexican people, who believe it or not are not a monolith. As Cardinal Dolan stated:
When we give in to our fears of the other because he or she is of a race different from ourselves, when we prejudge the motives of others precisely because they are of a different color, when we stereotype or ridicule the other because of racial characteristics and heritage, we fail to heed the command of the prophet Amos: “Seek good and not evil, that you may live; then truly will the Lord…be with you as you claim! …Then let justice surge like water, and goodness like an unfailing stream…”
Racism is actually a big deal. In our Church, it is a sin that therefore needs to be confessed by name. I understand that these teachers were likely not Catholic, but I’m glad to be part of a faith that decries their antics.
There’s also a broader question of whether politicking in an elementary school like this is acceptable or even ethical. This is fundamentally no different than teachers dressing up as Hillary Clinton and carrying signs reading “I’m with her.”
I suspect that the school district is quietly sympathetic to the teachers and therefore just keeping up appearances of finger-wagging at them.