Health and education officials across the country are raising alarms over wide underage use of e-cigarettes and other vaping products. The devices heat liquid into an inhalable vapor that’s sold in sugary flavors like mango and mint — and often with the addictive drug nicotine. They’re marketed to smokers as a safer alternative to traditional cigarettes, but officials say they’re making their way to teens with surprising ease. Health and education officials across the country are raising alarms over wide underage use of e-cigarettes and other vaping products. The devices heat liquid into an inhalable vapor that’s sold in sugary flavors like mango and mint — and often with the addictive drug nicotine. They’re marketed to smokers as a safer alternative to traditional cigarettes, but officials say they’re making their way to teens with surprising ease. A new wave of smaller vapes has swept through schools in recent months, officials say, replacing bulkier e-cigarettes from the past. It’s now common in some schools to find students crowded into bathrooms to vape, or performing vape tricks in class. “We’ve seen significant increases across the student body,” said Robert Keuther, principal at Marshfield High School on the south shore of Massachusetts. “This is not something specific to one group of kids. It’s across all of my grades, nine to 12. It’s all students.” Vaping devices are notoriously difficult to detect for schools, often leaving behind only a quick puff of vapor and a light fruity scent. Students get away with it in bathrooms, halls and even classrooms, where some say they exhale the vapor into their shirts. Although buying e-cigarettes is illegal under age 18 — and some states have bumped the minimum age to 21 — students say they can buy them online or from older friends. Some say there are dozens available for sale in school hallways at any given time. The rise of teen vaping has sparked concern among parents, politicians and federal health authorities, who on Tuesday announced a nationwide crackdown on underage sales of e-cigarettes. The Food and Drug Administration issued a warning to retail stores as part of its new operation against illegal sales. It also requested marketing and design documents from the maker of the Juul, a popular vape product that is shaped like a flash drive. The agency says it’s looking into whether certain features are specifically appealing to young people. Some schools have been inundated by the Juul, which dispenses a flavored vapor containing higher concentrations of nicotine than tobacco cigarettes. The device’s maker says it’s intended only for adults trying to quit smoking. Its website aims to block underage customers, and the company says it supports legislation to raise the minimum age for vaping products to 21 nationwide. But critics say the Juul’s sweet flavors and stealthy design seem to be aimed at kids. In an April 18 letter to the FDA, a coalition of medical and health groups called for a suspension of online sales until authorities create stronger rules against underage sales. Similar measures have been backed by school leaders including Keuther, who oversees 1,300 students south of Boston. “There’s a reason why it’s marketed that way,” he said, referring to the Juul’s concealable design. “We wish there was a way to curb that, because the industry is clearly targeting younger kids.” Many schools are pushing back with education campaigns against vaping. Health and gym classes feature new lessons on potential risks. Teachers are being trained on what to look for. Schools are producing online videos on the dangers of e-cigarettes.