By the end of this week, some 51,000 seniors will have graduated from New York’s public high schools, each with a minimum of 44 credits broken down in a formula guidance counselors know like a mantra: eight each in English and social studies; six each in science and math; two each in art and foreign language; four in gym; one in health; seven for electives, reports the New York Times. But exactly what qualifies for credit depends on the principals of the city’s 400-plus high schools, though they must follow certain state requirements, like the number of hours logged in class and evidence of student work and progress. And in an era of budget cuts in which both space and staffing are scarce, more and more students are earning some credits in unconventional ways: on Saturdays, in online courses, through independent study and in things like sailing that used to be considered extracurricular…