To participate in what’s known as the Community Eligibility Provision, the city had to change the way it calculated poverty. Officials now use “direct certification”: To be counted as low-income, a family must participate in federal public assistance programs, such as food stamps. Students from immigrant families are less likely to qualify for those programs, or even apply, experts say, given fiery White House rhetoric, President Donald Trump’s crackdown on illegal immigration and his administration’s threat to hold immigrants’ use of public assistance against them.