“Our investigation found that New York City’s elementary schools still are not ‘readily accessible to and usable by’ individuals with disabilities,” Mr. Bharara’s office wrote, “a population which includes not only students, but teachers and family members as well.”

The letter described the effect the violations had on families. Mr. Bharara’s office said that it had spoken with one family that had gone to what the prosecutors called “extreme measures” to keep a daughter enrolled in her local school, rather than subject her to a lengthy commute to the closest “accessible” school.

“A parent of this elementary school child was forced to travel to the school multiple times a day, every school day, in order to carry her child up and down stairs to her classroom, to the cafeteria, and to other areas of the school in which classes and programs were held,” the government wrote.

The alternative for children with mobility impairments was for the students to spend significant time traveling to a school that could accommodate their physical disabilities, the letter said.

“Requiring elementary students with disabilities to travel extensively at the beginning and end of each school day — a condition which is not imposed upon their peers — can impose particularly onerous physical demands on these children,” the government wrote.

The city had also not complied with the requirements of the disabilities law as to alterations made in schools since 1992, when the law went into effect, the letter noted.

In what it described as the most “glaring example of the city’s failure,” the letter cited the construction of an addition to a school in Queens in 2000 that was “riddled with inaccessible features,” like an elevator that was not the proper width, and noncompliant door knobs, bathroom “grab bars,” drinking fountains, sinks and faucets. The school also lacked visual alarms in classrooms, as required.