I don't think the admissions test should be scrapped and agree with the following New York Post editorial:

De Blasio’s plan to destroy New York’s top high schools
June 3, 2018

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Facing a long-known and genuine problem — the tiny percentage of black and Hispanic city public-school students who can pass the race-blind exam for entry into one of the specialized high schools — Mayor de Blasio opted on Saturday mostly for symbolism over substance.

And even the substantial change that he’s making is just redistribution — sending some kids to top schools at the expense of others — when he has a far better option: creating more good high schools to meet the demand.

The central complaint is that black and Hispanic kids make up nearly 70 percent of the public-school population, yet only 10 percent of the student bodies at the eight elite high schools. And girls outnumber boys in the larger system, while boys are a slight majority at the schools. De Blasio also notes that just 21 of the city’s 600 middle schools produced half the kids admitted to the “elite eight.”

One big thing he doesn’t say is exactly how the test is to blame — that is, how it unfairly discriminates.

In fact, the exam is just the messenger, pretty accurately determining which eighth-graders are actually prepared for the tough courses at Stuyvesant HS and the other elite schools. For the reasons so few black and Latino children do well on the test, you need to look elsewhere: to the K-8 schools, and to the level of family and community support for academic excellence.

Nor does he note that the big “winners” under the current system are East and South Asian-American children: Far more than whites, they are “over-represented” at the top schools. They’d inevitably be the big losers under his reforms.

Here is another piece on this topic from City Journal, a publication focused on urban issues:

The Plot Against Merit
Dennis Saffran
Summer 2014

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In 2004, seven-year-old Ting Shi arrived in New York from China, speaking almost no English. For two years, he shared a bedroom in a Chinatown apartment with his grandparents—a cook and a factory worker—and a young cousin, while his parents put in 12-hour days at a small Laundromat they had purchased on the Upper East Side. Ting mastered English and eventually set his sights on getting into Stuyvesant High School, the crown jewel of New York City’s eight “specialized high schools.” When he was in sixth grade, he took the subway downtown from his parents’ small apartment to the bustling high school to pick up prep books for its eighth-grade entrance exam. He prepared for the test over the next two years, working through the prep books and taking classes at one of the city’s free tutoring programs. His acceptance into Stuyvesant prompted a day of celebration at the Laundromat—an immigrant family’s dream beginning to come true. Ting, now a 17-year-old senior starting at NYU in the fall, says of his parents, who never went to college: “They came here for the next generation.”

New York’s specialized high schools, including Stuyvesant and the equally storied Bronx High School of Science, along with Brooklyn Technical High School and five smaller schools, have produced 14 Nobel Laureates—more than most countries. For more than 70 years, admission to these schools has been based upon a competitive examination of math, verbal, and logical reasoning skills. In 1971, the state legislature, heading off city efforts to scrap the merit selection test as culturally biased against minorities, reaffirmed that admission to the schools be based on the competitive exam. (See “How Gotham’s Elite High Schools Escaped the Leveler’s Ax,” Spring 1999.) But now, troubled by declining black and Hispanic enrollment at the schools, opponents of the exam have resurfaced. The NAACP Legal Defense Fund has filed a civil rights complaint challenging the admissions process. A bill in Albany to eliminate the test requirement has garnered the support of Sheldon Silver, the powerful Assembly Speaker. And new New York City mayor Bill de Blasio, whose son, Dante, attends Brooklyn Tech, has called for changing the admissions criteria. The mayor argues that relying solely on the test creates a “rich-get-richer” dynamic that benefits the wealthy, who can afford expensive test preparation.

As Ting’s story illustrates, however, the reality is just the opposite. It’s not affluent whites, but rather the city’s burgeoning population of Asian-American immigrants—a group that, despite its successes, remains disproportionately poor and working-class—whose children have aced the exam in overwhelming numbers. And, ironically, the more “holistic” and subjective admissions criteria that de Blasio and the NAACP favor would be much more likely to benefit children of the city’s professional elite than African-American and Latino applicants—while penalizing lower-middle-class Asian-American kids like Ting. The result would not be a specialized high school student body that “looks like New York,” but rather one that looks more like Bill de Blasio’s upscale Park Slope neighborhood in Brooklyn.