Children vaping in schools, teachers and health and education officials have warned. Children hide e-cigarette fumes under their shirts while smoking in hallways, bathrooms and even classrooms, the Associated Press reported.
The news comes just days after the US Food and Drug Administration (FDA) launched a nationwide raid on e-cigarettes, including efforts to stop its sale to minors online. 
"We have seen significant growth in the student body," said Robert Keuther, director of Marshfield High School, Massachusetts, to AP. "It's not for a group of kids, it's all my grades, nine to twelve, they're all students."
Juul e-cigarettes – a slightly concealable vaporiser in the form of a USB flash drive – came from teachers who did not Think of the sleek design and sweet flavors of the product, under attack aimed at minors.
"There is a reason why it is so marketed," said Keuther. "We wish there was a way to curb that because the industry clearly appeals to younger children."
The manufacturer Juul Labs claims on its website that it markets its products "responsibly and according to strict guidelines" (19659010) See all best photos of the week in these slideshows
On Wednesday, the Juul Labs a so-called "comprehensive strategy" to combat minors. The products, according to the website, are intended for adults who want to "switch" from traditional cigarettes.
Read more: E-cigarette users take high levels of cancer-causing chemicals, leading to traditional smoking
According to CDC vaping, some adults could benefit from completely replacing the normal cigarettes with the electronic variant. But they are not safe for children, young people, pregnant women and adults who are not already smoking, the agency notes.
The long-term effects of steaming are not well studied, but the product's aerosol may contain carcinogenic chemicals and flavors associated with severe lung disease. Juul uses fumes with a higher concentration of nicotine than conventional tobacco cigarettes, reports the AP.
Although some states have raised the minimum age to 21, many minors still get their hands on the devices. Students buy stolen vapes like Juul online and from older children in school corridors, the AP reports.
The FDA has launched a new initiative to eliminate the use of e-cigarettes by minors, including a "blitz" of certain Retail stores Facilities and efforts to restrict juul sales on the Internet to minors. "Protecting the youth of our nation from the dangers of tobacco products is one of the most important tasks of the US Food and Drug Administration – and I personally accept this commitment," said FDA Commissioner Scott Gottlieb in a statement.
Read more: Juul Vape: FDA Begins Nationwide Crackdown Against Product and Other E-Cigarette Brands
Vapes can also issue cannabis, causing several schools in New Jersey to ask students to take drug tests. Other facilities, including New York's Plainedge High School, have placed sensors that detect e-cigarette fumes in bathrooms.
Edward Salina, superintendent of Plainedge Public Schools, praised the sensors and told the AP, "The truth is the kids see it, they know what it is – and it's a deterrent in itself."
Juul Labs did not respond to a request for comment.