It's Thursday morning and 25 boys and girls are leaping on the spot in four lines, counting out jumping jacks in Hebrew.
"Echad! Shtayim! Shalosh!"
These are second grade students at the Hebrew Language Academy Charter School in Brooklyn, in which children - the majority of whom are not Jewish - study a large part of their curriculum in Hebrew.
When it opened last year, the HLA was only the second Hebrew-language charter school in America. Within a few years it could be among up to 30 such schools.
After the children reach 10, PE teacher Qayyim Shabazz shouts instructions in Hebrew to touch their shoulders, arms and legs or to run left or right.
Mr Shabazz points out the various ethnicities of his students.
"He's from Jamaica, he's from the West Indies, he's Jewish, those two are Mexican, she's from Haiti," he says.
Looking on admiringly, HLA principal Maureen Campbell says that most schools in her district are predominantly from one ethnic group or another but the HLA is diverse.
More than three-quarters of students have at least one foreign-born parent. About one-quarter of children come from Hebrew-speaking homes and one-quarter from Russian-speaking homes. Almost 40 percent of pupils are black.
Each class of 25 students in HLA, which will have 450 pupils from kindergarten to fifth grade by 2013, has two teachers, one who speaks Hebrew and one who speaks English.
Children have one hour of formal Hebrew instruction each day. Hebrew is also integrated into social studies, science, maths, music and physical education.
"There's no drill and kill," says Campbell. "No copying out words. It's total immersion."
The HLA was founded by 35-year-old Sara Berman, chairman of the Hebrew Charter School Centre, a nonprofit organisation that launched last year. It is funded by the Areivim Philanthropic Group, which is backed by several philanthropists, including Ms Berman's father Michael Steinhardt.
The HCSC aims to encourage Hebrew-language charter schools by providing start-up advice and grants. This year, awards total just over $1 million.
Says Ms Berman: "I am excited for every American child to have the education we are offering. I am also excited about the idea of Jewish students receiving this education. Over 50 percent of Jewish kids have no Jewish education at all. What we teach can be a platform upon which religious education can be taught."
The HCSC aims to help 20 Hebrew-language charter schools launch in the next five years.
One such school opened in East Brunswick, New Jersey, this month. More schools are planned in cities such as Phoenix, San Diego and Chicago.
Meanwhile, in Florida, a separate Hebrew-language charter movement has resulted in three schools with three more planned for the coming years.
Perhaps unsurprisingly, fee-paying Jewish day schools - the majority in America - are eyeing the Hebrew charter movement with concern. Charter schools, though privately run, are publicly funded.
But the American public school system, the equivalent of state schools in the UK, enforces a strict separation of church and state. So there has been controversy about whether Hebrew-language schools can avoid religion.
Says principal Campbell: "We can teach them about the holidays but not about the practices."
For some Jewish parents at HLA this is not an issue. Nearby Jewish community centres offer after-school programmes. Besides, says Tziona Royzman, whose daughter Maayan just joined the HLA, she prefers the diversity of the school to the yeshivah where she studied as a child.
"In a certain way I would say that we missed out in yeshivah because it's so old and traditional," she says.