The day before the city’s high school application deadline, Megan Moskop, high school admissions coordinator at M.S. 324 in Washington Heights, encountered a parent whose child wanted to apply to Baruch College Campus High School, a highly sought-after school in Manhattan with a 100 percent graduation rate.

Moskop had to explain to the family that the school is essentially off-limits to them, she said. It’s not that the student is low-achieving, Moskop said, but the family does not live in District 2 — and 99 percent of last year’s incoming class at Baruch came from that district.

The fact that students who live in certain geographic areas have “priority status” is just one way in which a system with over 400 high schools is, in practice, narrowed for students and families. By Thursday, when high school applications were due, Moskop said, many New York City students had likely abandoned their favorite schools.

“It’s almost, how quickly are the kids willing to give up on their dreams?” she said.

New York City’s high school choice process, which allows students to rank their top 12 schools, should make all schools available to any student regardless of where they live. But many roadblocks complicate that ideal.

By the time the deadline approaches, students at low-performing middle schools tend not apply to high-performing high schools, even if they have high test scores, according to a recent report by the city’s Independent Budget Office.

The system is notoriously difficult to navigate, particularly for students who live in low-income areas and have less help moving through the process. Some schools have geographic priority, some have academic requirements, and others ask students to provide information beyond what is actually needed.

Many families also hit snags when it comes to attending open houses or a high school fair. These can give students a leg up in admissions, but families often do not realize their importance until it’s too late, teachers and counselors said.

“They don’t go to the open houses,” said Gloria Carrasquillo, a guidance counselor at J.H.S. 151 in the Bronx. “They just have that application in a drawer or something.”

Another set of students may see options vanish because of their academic records. Many schools are “screened,” which means they accept students based on factors like grades, test scores and attendance. Families often have unrealistic expectations about whether their children will be competitive, said Elaine Espiritu, family impact coordinator at Brooklyn Laboratory Charter School.

Department of Education officials said they are working with middle schools and families to ease the process. This year, they added more information about the application process to the High School Directory, and launched a new website called SchoolFinder, which allows students to search for schools that match their interests.

“We’re committed to making the admissions process to New York City’s high schools easier for students and families and we are listening to the feedback of students, families, and guidance counselors,” said education department spokesman Will Mantell.

At Brooklyn Laboratory, Espiritu said families appreciated the new SchoolFinder app, and the school organized more than a dozen meetings to make sure families had as much information as possible. Still, the process can be tough, said Eric Tucker, co-founder and executive director of the school.

“We’ve worked hard to make sure that families have the tools to quickly get a kind of snapshot view of the kind of the data that matters most,” Tucker said. “But even then, this is an imperfect process because that amount of choice is overwhelming.”