The new admissions system will still weigh test results and grades, but, following a model pioneered in Chicago, it will also introduce ways to select applicants who come from poor and disadvantaged neighborhoods.

Under the new system, the applicant pool will be divided into eight groups based on the socioeconomic conditions of their neighborhoods. The admissions team will consider applicants within each group, admitting the top students in each tier in roughly equal numbers.

https://www.nytimes.com/2021/07/15/us/boston-schools-entrance-exams-admissions.html