A few minutes earlier, they had analyzed a sign exhorting dog owners not to permit their animals to relieve themselves near a certain building. Next, a picture of Theodor Herzl, the father of Zionism, with his famous mantra, “If you will it, it is no dream,” twisted into “If you don’t want, you don’t need.” Here, a verse by the street artist and poet Nitzan Mintz. There, the iconic image of a forlorn child from the Warsaw ghetto, captioned “Don’t Deport Me,” repurposed to the current crisis of migrant workers from Africa flooding south Tel Aviv.

“They depend on a cultural knowledge that you don’t necessarily have,” said one of the students, Marcela Sulak, who has been here two years as director of the creative writing program at Bar-Ilan University. “He teaches you the tools so you can figure it out on your own. You’re learning the Hebrew you need every single day by looking at the neighborhood.”

The hourlong classes, which cost 50 shekels, or about $12, are organized on Facebook. They grew out of last summer’s protests, when Mr. Sharett’s traditional Hebrew students were mystified by the signs at the encampment along Rothschild Boulevard, so he started taking them — and his little white board — outside for lessons. After the protest tents came down, he decided to make the graffiti-pocked walls of his gentrifying neighborhood the new syllabus.

“It’s not only to teach language, it’s also to teach the culture,” Mr. Sharett explained. “Someone took a line from a song we all know and changed one word; it’s very hard to understand that if you don’t have someone local to explain, ‘That’s a take on...’ ”

Mr. Sharett, 40, has a day job at a television company, but has been giving private Hebrew lessons for several years. Besides the graffiti course, he offers one-offs touring the city’s spice market (“Wake up and smell the Zatar”); shopping and cooking with a famous chef (“While chopping, we learn the names of the vegetables”); and watching the local version of “American Idol,” with frequent use of the pause button to translate slang and jokes (“This is Israeliness 101,” he said).