The Chicago Teachers Union approved a plan Wednesday to close down city schools on April 1.
The union wants to bring attention to education funding and contract issues. Earlier this month, the district said employees must take three unpaid furlough days during the current fiscal year to save $30 million.
Chicago Public Schools officials say a walkout would be illegal, because it isn't in line with the state-mandated process for a teacher's strike.
The district faces a $1.1 million budget deficit and is receiving no income from the state due to the current budget impasse between Republican Governor Bruce Rauner and the Democratically-controlled legislature.