Kevin Quealy and Eliza Shapiro:

Every fall, tens of thousands of New York City students sit for a high-pressure exam that determines their admission into the city’s most selective public high schools. Those students have three hours, a race against the clock to answer questions on subjects like trigonometry and to analyze reading passages.

But a few hundred students have double the time to take the exam, and there appears to be a racial disparity in who is receiving this special accommodation, which is covered under a federal designation known as a 504. The designation is meant to give students with mental and physical disabilities — whether attention deficit disorder or a broken arm — a fair shot in public education.