By Stephanie Banchero, Chicago Tribune Knight Ridder/Tribune Business News
Dec. 10--Chicago Public Schools chief Arne Duncan threatened Thursday to sue the U.S. Department of Education, after the agency barred him from using federal funds to run a tutoring program for 40,000 struggling students.
Calling the decision a "slap in the face" to the district, Duncan said he would "go to the courts, go to Congress, go wherever we have to go" to appeal.
"We're not backing down because this tutoring program is so important to our children," Duncan said at a news conference. "We hope we can sit down and talk with them and that cooler heads will prevail."
On Wednesday, federal officials …