In a classroom on Camp Ramah’s sprawling campus, nestled against the mountains of Ojai, a bearded rabbi moves enthusiastically between tables of chattering children.

Spread on the tables are small, origami-like black boxes; leather straps; long, white calf hairs; and Ziploc bags containing parchment scrolls inscribed in Hebrew.

Rabbi Noah Greenberg darts around the room, calling out names of Torah passages, asking questions about their meanings, and helping students roll up the parchment and wrap them with the calves’ hairs.

“Be very, very careful not to mix up your [scrolls] with your neighbors’,” he instructs. If the scrolls get mixed up, he explains, the tefillin will “not be kosher.”

For the past eight years, Greenberg —an Orthodox Jew and a craftsman — has been traveling between his home in Israel and the United States to teach bar and bat mitzvah-age children of all denominations how to prepare for and perform one of the most important mitzvot: tefillin.

Sometimes called phylacteries, tefillin consist of two small black boxes containing Hebrew scrolls on which four specific Torah passages (Kadesh, Vehayah Ki Yeviacha, the Shema and Vehayah Im Shamoa) are handwritten. Traditionally, beginning at age 13, observant Jewish males strap the tefillin onto their head and upper arm each weekday. In recent years, some girls (primarily in the Conservative movement) have begun wrapping tefillin, too.

For about 15 hours over the course of a week, Greenberg guides his students through the making of their own tefillin. The children create the boxes from goatskin parchment pre-cut from a template: They fold the parchment into the box shapes, emboss the Hebrew letter “shin” in the leather and spray-paint them black. After rolling, wrapping and inserting the scrolls, they sew the tefillin box closed using thread made of animal sinews and attach the straps using specific knots.

At the end of the week, the children don their handmade tefillin for the first time and recite the Shema during a special ceremony.

The program is called Kesher Tefillin (“kesher” means connection; the goal is for the students to connect with the ritual and its meaning). Greenberg said he has worked with nearly 4,000 children at camps, schools, synagogues and in private groups. Each summer since 2008, he has traveled to Camp Ramah in Ojai; this summer he held two sessions there, where a total of 70 children made tefillin.

“It’s incredibly moving. … This project is teaching them about sanctity, about sacredness, about reverence,” Greenberg said. “And they really get it. At the end — this amazes me every time — the most boisterous of them, the most problematic of the children, those are the ones that take this the most seriously.”

Although commercial tefillin are made using hydraulic presses and computer-controlled machinery, Greenberg thought there must be a simpler way to construct them.

“Moses in the desert put on tefillin,” he said. “Obviously, he didn’t have hydraulic presses.”

Greenberg created a prototype design, which he showed to Rabbi Loren Sykes, founding director of Camp Ramah Darom in northeast Georgia. Sykes encouraged Greenberg to pilot a tefillin-making program at his camp, and the project took off.

Greenberg brings his own tools and materials to each session. The goatskin parchment is thinner than the thick leather typically used for machine-manufactured tefillin. Store-bought tefillin can cost several hundred dollars, but the materials for Greenberg’s tefillin cost about $200, according to the program’s website.

By making the tefillin themselves through a guided process, the rabbi explained, students understand their meaning on a much deeper level than if they had simply purchased them.

“When young people, or anybody for that matter, are busy and they’re having fun and they’re challenged, you can teach them anything and they don’t even know they’re learning,” he said.

Rabbi Joe Menashe, executive director of Camp Ramah in Ojai, said that every year, more children want to participate in the tefillin program than there are spaces.

Jonah Tochner, 13, of Los Angeles, participated in the program this summer. “I thought it’s such a cool opportunity,” he said. “I chose this because I can do sports pretty much the whole year, and you literally can’t do this anywhere else.”

Micah Ross, 12, of Lafayette, said she had tried putting on tefillin once, but never owned her own pair.

“I know I probably wouldn’t get one if I didn’t make it,” she said. She found the program “fun and interesting,” adding that you “have to be focused and really listen.”

Parents have been impressed with the program, too. Duke Helfand of Los Angeles said his three sons all have participated. His eldest son, Max, still wears his tefillin five years after he made them, Helfand said.

And, for Greenberg, Kesher Tefillin goes beyond the mitzvah of tefillin.

“It’s about a holistic presentation of Jewish life and tradition,” he said. “Because we have the wherewithal to discuss everything and anything in Judaism, [the students] come away with a totally different perspective of who they are as Jews, and where their place is in the Jewish world, and what their relationship is with the commandments.”