This is math. No one is groaning.

Some would call the scene a miracle.

It's 3:45 on a Tuesday afternoon, and this group of seventh-graders doesn't want to go home. School was dismissed at 2:30, but they've been here for the last hour, bouncing on the edge of their seats and peppering their teacher, John Johnson, with questions. Atomic mass and photosynthesis are hot topics, as is trying to understand how Rutherford's model of the atom differs from Bohr's.

The pace is breathless and there's a sense of urgency as Mr. Johnson covers the black board with formulas, enthusiastically extols the genius of Newton, and calls students to the front of the room to help illustrate the laws of motion.

But finally he's had enough. "It's time to go home," he roars good-naturedly at them. "Get outta here!"

"No, no!" they protest. "It's early. Fifteen more minutes!"

In an era when educators agonize over how to interest more children -especially minorities and girls - in math and science, an instructor like Johnson presents the most basic and immediate of solutions: good teaching.

The setting is IS 53, a public middle school in what could easily be called a disadvantaged section of Brooklyn. More than 70 percent of the children in this school live at or below the poverty level.

But they have a powerful asset working for them in their lives: John Johnson. And they're well aware of it. Ask what's so special about this particular math and science teacher, and the kids bubble over with enthusiasm.

"He makes it fun to learn." "He cares about us." "You're never shy to ask him a question." "He stimulates our minds and makes us think."

Johnson's style in the classroom is a curious mix of boot-camp sergeant, stand-up comedian, and earnest scholar. When the students report for their 8:30 a.m. math class after a three-day weekend, there's no gentle transition back to academics.

They're barely seated before the first problem is on the board and they're bent over their desks graphing linear equations. "I don't want to talk about the weekend with them," he says. "Look, they're kids. If you let them, they'd talk to you about the weekend all day. This is business."

As the kids scribble earnestly in their notebooks, racing for the answer to the problem, Johnson gently taunts them. "What, are you going to take all day on this?" he asks. "This is easy."

"It's easy for you," protests one petite scholar. "You went to college."

"And that's just where I'm trying to get you, girl" Johnson shoots back at her.

To watch Johnson in the classroom is to imagine that he was born to the job. In fact, he's only been teaching for the past 11 years, after putting an early end to a career as an accountant on Wall Street.

"I came to teaching out of self-interest, not altruism," insists Johnson, who is a native of Guyana but has been living in the US since college. He says he became fearful of the instability of the stock market and wanted to find a job with more security.

"But the biggest surprise for me was to find out how much I like this," he says.

One of the ironies of Johnson's story is that he does not have a particular academic concentration in math or science. In fact, he says, until high school, "I considered myself an abject failure in math." A positive high school experience, he says, helped turn that around and he came to enjoy the subject.

But when he arrived in New York in the 1960s to attend City College he chose to major in economics and philosophy. Economics strengthened his math abilities, he says, but he credits philosophy with giving him the "higher-order thinking skills" he feels have helped make him a good teacher.

Johnson later went on to do graduate work at Columbia University. He's now midway through a PhD program in education management there, but has taken a break to help one of his three children get through medical school first.

Like his after-school sessions, the pace in Johnson's classes is quick. His chalk-covered fingers fly as he scratches out problems on the board. Hands are in the air constantly begging Johnson to check students' work, to tell them if they did it right, to pay them some attention. "Tell me your answers so I can laugh at you," he dares the class, but nobody seems scared. On the contrary, many are smiling.

Johnson manages to give his students a lecture, but in the course of it there's so much give-and-take, so much rapid-fire questioning and answering, and so many chances for them to actively participate in problem-solving, that they hardly seem to realize it. When the bell rings, some moan with disappointment.

"The children adore him," says Linda Adler, his teaching partner. "He gives completely of himself."

Johnson and Mrs. Adler both teach a group of specially selected seventh-graders who have achieved high scores on standardized tests. The goal at this point is not so much to focus on test scores as to prepare these kids for entrance exams to New York's most selective public high schools, and to help orient them toward higher ed.

Last year, 100 percent of the IS 53 students who had studied math with Johnson passed the N.Y. State Regents math test, compared with 75 percent citywide.

"A few years ago, we sent more students to the special high schools than any other school in the district," says IS 53 principal Charlotte Powell. "Much of that was because of Mr. Johnson." She considers him one of the two most talented teachers she has ever seen in more than 20 years in public schools. "Any school in any city in any state would want a teacher like him," she says.

What seem to amaze his colleagues most are the after-school tutoring sessions. Although he receives no pay for his time, Johnson stays till 4 p.m. twice a week. Attendance is voluntary, but as many as 15 to 25 students typically show up. Occasionally, students from other schools in the district appear. They've heard about Johnson and want to join in. They are welcome, Johnson says. "I tell kids anyone can come - as long as they want to work."

Veronica Gonzalez, one of Johnson's students, is a bit breathless as she leaves this afternoon's tutoring session. "It was great," she says. "I learned so much."

Not many teachers would be willing to give as much, says I.S. 53 assistant principal Burt Schindle. "He's extraordinary. But it's how he is as a human being. He sees everything, everything, in terms of the children."

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