In what is likely to be the area’s largest education-related rally in months, about 600 parents are expected to gather today in Lower Manhattan to demand an overhaul of the city’s public middle schools.

Officials including the president of the teachers union, Randi Weingarten, and the chairman of the City Council’s education committee, Robert Jackson, are scheduled to join a march to the Department of Education headquarters from St. Paul’s Chapel nearby in Lower Manhattan.

The event is timed with the release a new report disputing Mayor Bloomberg’s claims that racial and economic achievement gaps have closed under his watch.

“In a crucial part of the school system — the middle grades — the gap is not closing,” the report, from a group of parents across the city, the Coalition for Educational Justice, says.

Mr. Bloomberg zeroed in on the middle-school years in his State of the City address last week, vowing to raise standards for exiting eighth grade and to implement recommendations from a task force on middle school led by the council speaker, Christine Quinn. Parent leaders at the Coalition for Educational Justice yesterday said Mr. Bloomberg’s mention was not satisfactory. “There didn’t seem to be a concrete plan, which is a little surprising,” a Brooklyn parent, Zakiyah Ansari, said. “We really thought there would be some more recommendations being drawn from those that the task force wrote.”

In the report, the parents push for three initiatives they said are drawn from months of research and visits to successful schools.

To make time for enrichment programs like art and advanced classes, such as Regents courses, they want to add 90 minutes to the school day. To improve teaching quality, they want to create a program at certain schools that would lessen the course loads for first-year teachers and build mentoring systems for all teachers. Finally, to build in more emotional and social support, they want create “student success centers” staffed by one professional counselor for every 200 to 250 children.

The report suggests paying for the programs with Governor Spitzer’s Contracts for Excellence program, which offers funding for specific goals, including improving teaching quality and extending the school day.

The report makes a case that black, Hispanic, and poor students fare the worst in middle schools, describing flat or widening differences in performances on state and national reading tests.

Although about 60% of white eighth-graders meet state reading and writing standards, about 30% of black and Latino eighth-graders do, a gap that has increased five percentage points since Mr. Bloomberg began reorganizing the public schools, the report says.

It also shows that high-poverty schools have fewer teachers who hold certifications in the subjects they teach than low-poverty schools.

A Department of Education spokeswoman, Debra Wexler, provided state reading and math data from between 2002 and 2007 showing a gap between the portion of white and black and Hispanic students meeting standards closing by about 4 percentage points.

Ms. Wexler also outlined a half-dozen initiatives the department has undertaken to target middle schools, including an extra investment of $89 million this year; a research project; new regular diagnostic tests, and financial incentives to encourage high-performing schools to admit low-performing students as transfers.