Mamdani would be the fourth consecutive New York mayor to implement major changes to G. & T., which offers accelerated and enriched curricula to qualifying children. Until the mid-two-thousands, a patchwork of G. & T. programs operated all over the city, with widely differing admission criteria. Then, under Michael Bloomberg, the city introduced standardized criteria for G. & T. admissions: exams, administered in testing centers to four- and five-year-olds. A child who landed in a percentile in the high nineties might secure an extremely coveted seat at one of five citywide G. & T. schools. A result in the mere low-to-mid-nineties might qualify a student for one of the more numerous district-level G. & T. programs, which are housed in regular schools. A seat in G. & T. can put a kid on track for admission to New York’s equally coveted specialized high schools and, by extension, to the nation’s élite colleges and universities. But there were always more eligible kids than seats, and final placements were mostly determined by lottery.