By Mary Wisniewski

CHICAGO (Reuters) - Starting this week at Nash Elementary on Chicago's west side, students are getting up to 23 minutes more of math and 27 minutes more of language arts.

At Disney II Elementary on the north side, children have more time for special classes, so the music teacher is now there all day.

These are two of 13 Chicago public schools that are early adopters of a plan to add 90 minutes to the school day by next year, a change pushed by new Mayor Rahm Emanuel who says it is necessary to improve education.

But the way Emanuel's administration has pushed the plan has rankled the Chicago Teachers Union, which has already seen his new school board vote to rescind an annual 4 percent teacher raise.

The controversy, one of many between government bodies and teachers' unions around the country, promises to lead to testy contract talks in 2012.

"We have a real problem with the way this is being done," CTU President Karen Lewis said. "Rahm Emanuel is not the mayor -- he's the emperor."

Emanuel has said that Chicago Public School students spend 15 percent less time in the classroom than the average American public school student. The union, however, has questioned how the city counts the time, noting that Chicago schools have more instructional time than those in New York or Los Angeles.

To get schools signed on early, Emanuel offered a cash bonus of $150,000 each, plus a bonus for teachers of about $1,250. The union saw this as a strong-arm tactic, Lewis said. It sued the school board for unfair labor practices before the Illinois Educational Labor Relations Board.

Lewis said the union knew the longer day was coming, but wanted it planned appropriately, and wanted teachers fairly compensated.

"Are we going to have more mind-numbing test prep?" Lewis asked. "We want to make sure our kids (get) 90 minutes more of broad, rich, deep curriculum."

Chicago schools CEO Jean-Claude Brizard said early adopters could help illustrate what issues need to be addressed when the longer day goes systemwide next September.

CHANCE TO CATCH THEIR BREATH

Educator Deborah Meier, a senior scholar at New York University, said teachers did not need more time in front of classrooms -- they needed time for professional collaboration and for their own families. She noted that teachers already spend hours on preparation and grading.

"The motives of this sound to me like it's partly to weaken the union," said Meier, who has spent 50 years in schools as both a teacher and a principal.

Barbara Radner, director of the center of urban education at DePaul University, said both sides needed to collaborate on a longer and a better day.

Radner, who has unofficially consulted with schools on the longer day, said the new schedule would allow teachers to have a 45-minute lunch in the middle of the day, rather than at the end, and would open up time for recess.

"They put that break in the middle of the day so teachers have a chance to catch their breath, talk to each other and get ready for the afternoon," Radner said. "We have restored civility to the school."

CPS spokeswoman Becky Carroll, asked why CPS was offering incentives for early adopters, said: "If you're sick and you know in a year there's going to be medicine to help you, why wait?"

Is the medicine effective? A review of research on the longer day suggests that extending school time can help students learn, particularly at-risk students, but research designs were weak, so it was hard to tell what was helping.

"It seems likely that there's a small positive effect in extending time, particularly for particular groups," said Erika Patall, assistant professor in education psychology at University of Texas at Austin and one of the authors of the review. "It's possible that there's no effect."

Brizard said he knew a longer day alone was not a panacea, but that it would provide teachers extra tools, like more time for literacy and art.

"We just really would like to see our students not only performing strongly in the core academic areas, we would like to have students become strong artists, performers," said Bogdana Chkoumbova, principal at Disney.

As for public opinion, Chkoumbova said: "I am yet to hear about a family that is opposing the longer school day."

(Writing and reporting by Mary Wisniewski, Editing by Cynthia Johnston)