They were already taking Advanced Placement calculus, history, English and Spanish.

But they wanted more.

Advanced Placement chemistry.

There was, however, one small problem: Mater Academy Charter High School wasn't offering the class.

So the handful of homework-seeking, self-proclaimed overachievers came up with a solution.

They would teach it to themselves.

The class, offered in high schools throughout the country, is among the most difficult a kid can take. Students who score high on the Advanced Placement exam can earn college credit.

``I'm not too worried, though,'' said Michael Rodriguez, the 16-year-old leader of the group, with an air of confidence. ``It's not that hard.''

The AP chem students meet every seventh period. Sometimes, they gather in the school media center. Other times, they're in a chemistry classroom.

They spend the beginning of their class reading from collegiate textbooks -- the kind with tiny print and complicated diagrams. Later, they discuss what they've read -- and make sure everybody understands.

The teens stay on task, even without a teacher keeping watch.

On a recent Wednesday afternoon, they chatted about aqueous solutions.

``OK, so we are talking about dissolving here,'' said Andy Rodriguez, Michael's twin brother and a member of the study group. ``Let's look at some examples.''

INDEPENDENT STUDY

Creating the independent-study class was Michael's idea.

Last spring, after completing Advanced Placement biology, Michael was debating which science class to take next. In most educational programs, chemistry follows biology. But Mater, an A-rated school in Hialeah Gardens, didn't have the resources to offer AP chem.

Michael, then a rising junior, assembled four of his classmates and made his pitch.

At first, the idea met some resistance.

``We had teachers who were like, `You have a lot on your plate. This might be a little much,' '' Michael recalled.

But the teens were undeterred.

They called for a meeting with Kelly Gimbel, a science teacher who minored in chemistry at Florida State University.

Gimbel offered her support, both as an advocate for the teens and an academic tutor.

``I could tell that they wanted it -- and that they were willing to work hard,'' she said.

Gimbel now pitches in by demonstrating chemical reactions in the science lab.

She also provides the teenagers with notes on the chapters.

Sometimes, at the students' request, she gives them quizzes and homework.

``They're always asking for more,'' she said, laughing.

The boys' friends say they've come to expect this kind of ambition from the Rodriguez twins.

`NORMAL FOR THEM'

``This is normal for them,'' said Jasser Trujillo, 17. ``They're really smart.''

Michael aspires to study mathematics at the Massachusetts Institute of Technology. Andy has an interest in engineering. Their friend Steve Toro wants to attend Miami Dade Honors College and the University of Florida.

But for now, they're each focused on acing the Advanced Placement test in May.

Although the group was once made up of five teenagers, it has since been whittled down to three.

The reason?

``Stoichiometry,'' Michael explained, referring to the art of balancing chemical equations. ``It was killer.''