Here’s how you know that Chicago authorities are expecting a rowdy turnout at a mass rally called for Wednesday afternoon to protest the announced closings of more than 50 schools this year: Security staff have already erected barricades around the Board of Education in downtown Chicago, and authorities sent a memo to school principals telling them to report on protesters and their actions.

Thousands of people are expected to protest  last week’s announcement that 54 under-enrolled schools will be closed before this fall to help close a $1 billion deficit in the country’s third largest district. It is the largest mass district closing of schools ever in the United States, and it is fiercely opposed by many teachers, parents and education activists. The vast majority of students affected are African American and Hispanic, and all but one of the schools scheduled to be closed are elementary schools. Small groups of parents and students have already staged protests in the last week.

The memo, released by the Chicago Teachers Union, told principals how to handle the protest. The union reported that it said:

Be approachable and supportive to feelings of unrest, anxiety or dissatisfaction. Observe and report all information regarding possible protestors, locations, dates and times… Is the media present? Which news outlet(s)?

In fact, the union this month, in anticipation of the closings announcement, co-sponsored training in protest techniques, including disruptions, occupations and arrests, according to a union press release. The trainings were led by political activist and scholar Lisa Fithian, who for decades has been a student, labor and community organizer on a range of issues.

Karen Lewis, president of the teachers union, reacted to the memo sent to principals by saying in a statement, “Why are they asking principals to work as agents of this administration when they are the ones who have created a climate of chaos? Civil disobedience is a direct response to unjust policies and practices. We intend to use whatever nonviolence protest actions we have in this fight for education justice.”

A union press release says that the Wednesday protest “could be the spark of [a] 21st century Civil Rights Movement in Chicago. Stay tuned.