Not a good signal
Many of us are sympathetic to folks who wish to come to America to find a better life. Many of us who are descended from immigrants of a century or two (or three) ago still cling to a fondness for the "mother countries" of our ancestors. However, most of us do not want to turn America into what our ancestral countries are or were. A visible symbol like this one at Montebello High School in Montebello, California, sends the wrong message altogether.
It should be noted, however, that this was not the act of students of that school.
"On Monday, March 27, 2006 at noontime, a group of students from neighboring school districts to the east of Montebello (i.e. El Rancho Unified School District and Whittier Union High School District) marched to Montebello High School (MHS). At this time, MHS was on lockdown and the students remained in their classrooms. The other students, from outside Montebello Unified School District, who were estimated to be 800-1000 strong, gathered outside the MHS campus. For a brief time, the school flag was lowered, replaced with a Mexican flag, and the American flag flown beneath, upside down. The California flag was subsequently stolen. It is important to emphasize that this was not the act of any Montebello High School student."