Nicole Johnson’s 5-year-old son Zane, who is autistic, has a morning routine he likes to follow: He and his mother get up, get dressed, and then, when the school bus rolls past their Bronx apartment building, his school day begins.

More than a week into the new school year, the routine Zane has followed from age 1 has been interrupted: The buses drive by, but Zane stays at home.

Ms. Johnson said the reason is that the school the Department of Education placed him in, P.S. 168 in the Bronx, told her a few weeks before the start of the school year that it has no space for Zane.

Since then, she has been scrambling to find an alternative — so far to no avail.

Special-education advocates said yesterday that Zane is not the only child lacking a spot in school this year.

“It seems to be a pattern,” the special-education policy coordinator at Advocates for Children, Maggie Moroff, said. “They’re going to their schools with placement letters, kids with special needs, and the schools are saying, ‘We don’t have room; we don’t have room in the class that you were promised.'”

Ms. Moroff said she has heard of at least 40 students without spots and suspects there are even more whose families are not savvy enough to seek the help of Advocates for Children or another outside group.

The president of the city teachers union, Randi Weingarten, said the union is considering filing complaints with the state Education Department about the flawed placements.

The city’s public advocate, Betsy Gotbaum, visited a Bronx center last week where parents with registration problems have been lining up in search of information.

She said in an interview that she counted between 100 and 115 people who were standing outside the building hoping to get inside.

“Many of them had in their hand these sheets of paper that said your kid should go to P.S. whatever, and they had taken their child to that school, and they told them there was no place,” Ms. Gotbaum said.

Parents said they often spent more than two days standing in a line that snaked outside the door and then around the corner of the building, 1 Fordham Plaza. They said they would wait all day, only to be told to come back the next day — or to get a placement that would not pan out, putting them back at square one.

Sabrina Yaw, a single mother of seven children, said she arrived at 1 Fordham Plaza after her son Damaani spent what was supposed to be his first day of sixth grade sitting in the main office because there was no space for him in the special-education class to which he had been assigned.

Ms. Yaw said the first placement she received would have placed her son, who has a behavioral disability but no academic difficulties, in a class with children with Down syndrome.

She said she is visiting a second option today that she hopes will work out.

A spokesman for the Department of Education, Andrew Jacob, said some special-education students have not yet found placements, but that many of the families fighting for spots already have been given acceptable options; they are just searching for schools they would prefer.

Ms. Johnson said she wants the city to build more schools. “They’re building another Yankee Stadium and you don’t even have enough schools for kids,” she said.