I wouldn't be so quick to judge. Reading the article, this part leapt out at me:
A Texas high school student has filed a federal lawsuit against her school after her Spanish teacher allegedly gave her a failing grade for refusing to recite the Mexican pledge of allegiance.
[...]
The complaint also states that the student was not allowed to recite the American Pledge of Allegiance in Spanish in front of the class as an alternative assignment. The teacher, Reyna Santos, gave her a different assignment on the Independence of Mexico to which she received 13 out of 100 points.
Now, without seeing the assignment in question, I can only speculate as to what the students were actually asked to do. But from the sounds of things, this was a civics class. I don't know what it's called in America, but down here it's known as Human Society and Its Environment (HSIE), and covers the social sciences - history, geography, etc.
This is what I suspect has happened: firstly, the girl refused to recite the Mexican pledge of alleigence, and the alternative assignment was on the Independence of Mexico. So they were probably studying Mexico, which is supported by the idea that reciting the American pledge of alleigence in Spanish would not meet the requirements of the assignment, since it has nothing to do with Mexico.
I very much doubt that the students were being forced into reciting the Mexican pledge of alleigence, as if their teacher was secretly recruiting an army of teenagers to Mexico. Rather, one of the key concepts that students in Year 9 should be familiar with is the idea of citizenship, and the position and role of their nation in a regional context. Again, I'm going by the Australian curriculum here, and I'm making a huge assumption, but I have to go off what I know, and that's what I'm seeing here. If I were setting this assignment, I'd probably be asking students to look at the American and Mexican pledges of alleigence, paying particular attention to the values each pledge displays, and how those values could go about shaping a national or cultural identity. This would naturally require students to be familiar with the Mexican pledge of alleigence, and some of them may choose to recite it, particularly if there was an oral component to the assignment (and there may well have been, since modern teaching theories are designed to take into account a variety of learning styles).
If someone can direct me to the syllabus used by the school, I can probably give a much clearer idea of what might have been expected in the assignment.