For St. Paul public schools, finding substitute teachers has been a struggle — actually, "a nightmare," according to Superintendent Valeria Silva.

So, to ease the last-minute scrambling and improvising, the district is turning this year to a private firm, Teachers On Call, to manage its day-to-day substitute operations.

Teachers On Call handles that role for 42 districts in Minnesota, and so far this year, the partnership has produced mixed results for St. Paul. The firm has managed to put more substitutes in the schools, but also left a greater percentage of slots unfilled. A key reason: Requests for substitutes have been on the rise in the district, from 2,346 in September 2013 to 2,836 in September of this year, a 21 percent increase.

"I would say that Teachers On Call has gotten off to a good start, but there is work to be done," Laurin Cathey, the district's human resources director, said last week.

At St. Paul Federation of Teachers headquarters, Nick Faber, the union's vice president, said anecdotal reports point to continuing frustration at the school level, with some teachers who had been excused for professional development purposes being called back to classrooms when substitutes weren't found.

"From our teachers, it sure feels like it's not any better," Faber said of the situation, which has prompted the union to begin tracking unfilled absences.

In 2012-13 and 2013-14, St. Paul turned to outside companies to help it fill slots on days when the district went through its pool of substitutes and came up short.

Teachers On Call filled that supplementary role in 2012-13, and proved a reliable supplier of 35 to 40 substitutes per day when the district hit its daily "tipping point" of absences, which Cathey put at 200 teachers.

The district used a different firm in 2013-14, and during the final five months of the school year, ended up with a total of 829 slots going unfilled. Often, teachers then must be pulled from training sessions to fill the slots. Sometimes, principals are forced to take creative action, such as rotating in other teachers with time available in a given day.

This summer, when the school board took up the Teachers On Call proposal, Silva spoke of receiving calls from schools frustrated by unfilled absences and of the perceptions of some people that the district wasn't providing substitutes in order to save money.

"The reality is we don't have people," she said.

The plan, as approved by the board this summer, called for St. Paul's pool of 760 substitutes to be employed by Teachers On Call — 305 substitutes ultimately signed on with the company as of Aug. 29 — and paid the same $13.75 to $15 per hour they earned for the district. The teachers could continue to work in St. Paul schools, and Teachers On Call would pull from its broader pool of substitutes to help fill additional absences, Cathey said.

For its work, Teachers On Call is being paid a $20,000 one-time setup fee plus 25 percent of a substitute's hourly pay. For example, a teacher who earns $15 per hour makes $115 a day. Teachers On Call would collect $143.75 from the district, pay the teacher $115 and keep the $28.75 balance.

If all goes as planned, Teachers On Call would earn $750,000 of the $3.9 million that the district budgeted for substitutes in 2014-15, up from the $2.4 million spent last year.

During the first two weeks of September, Teachers On Call filled 95 to 100 percent of absences each day, Cathey said. But by month's end, as more teachers took sick days for themselves or family members, or left class for professional development purposes, such as iPad-related training, Teachers On Call ended up filling 88 percent of the substitute positions needed — down from a 95 percent fill rate a year ago.

The district, in turn, has decided to cancel most professional development activities through November "as a way of reducing the daily need," Cathey said.

As for Teachers On Call, Cathey said that the company's ability to fill more jobs in September than the district did a year ago — 266 more positions, for a 12 percent increase — could be a sign they're better at the work than the district.

But the true test, he said, will be in how well the firm continues to build its pool, something the district felt that Teachers On Call definitely was in a better position to do.

Anthony Lonetree • 651-925-5036