Two days after being blindsided on the Q Comp issue, St. Paul Public Schools negotiators walked out of a negotiation session with teachers Thursday, saying they instead will seek to take the talks to mediation.

Matt Mohs, the district’s chief academic officer, acknowledged that the move comes early. Mediation typically is needed to “get across the finish line,” he said. But negotiators concluded the talks over a new teachers contract had been unproductive, and the union’s wide-ranging “wish list” would bankrupt the district.

On Tuesday, the St. Paul Federation of Teachers informed the district it would not join in developing a Q Comp alternative teacher pay plan. The union detailed its reasoning to members and reporters, but declined to give an explanation to district negotiators.

Asked how the union’s Q Comp refusal figured into the district’s decision, Mohs said that it “probably [was] the final straw.”

Last spring, the union presented a two-year contract proposal seeking a continuation of the “steps and lanes” basing teacher pay on seniority and education levels, plus provisions to make preschool available to every 4-year-old and standardized tests a requirement for no one, among other goals.

The district said that requests such as the proposed opting out of the Minnesota Comprehensive Assessments (MCAs) were outside the bargaining process.

On Thursday, the two sides had been scheduled to meet in a 5 p.m. negotiations session at Benjamin E. Mays International Magnet School. The public event drew dozens of union members wearing red T-shirts. But the talks never started. Instead, Margaret Skelton, the district’s lead negotiator, read a brief statement announcing the planned move to petition for mediation.

Union members responded with scattered boos.