Sydney Kramer has a full plate of history, English, science and math assignments each week. But, unlike her classmates, she’s also squeezing in a few lessons on e-commerce and the bottom line.

Just 12, Sydney already has two short paperback mystery books to her credit, and a third book is on the front burner.

She may not be a best-selling author like Harry Potter creator J.K. Rowling, but she certainly has grand ambitions — book royalties, Oprah appearances and spinoff products and ventures.

“I want to make big money,” said Sydney, an energetic sixth-grader who carved out time after school recently for a telephone interview. Her home in Downingtown, Pa., also doubles as corporate headquarters for her business, Cookie Dalmatian Mysteries. The middle schooler’s first self-published book, The Case of the Missing Prom Dress, came out in 2004. It features Cookie the Dalmatian, a four-pawed supersleuth who searches for a dog that stole his girlfriend and some prom dresses.

Her second book, The Diary of Ms. Jane French Bull, was completed a couple of months ago just before the holidays. This plot again revolves around Cookie, who tracks down a stolen diary that contains his family’s most important secrets.

About 100 copies of the first book have been sold — Sydney’s grandmother was her first customer — and sales of the sequel have hit about 30.

Sydney is one of a growing number of young entrepreneurs starting and running businesses with varying degrees of success. Although figures are elusive, Young Money magazine executive director Todd Romer estimates that tens of thousands of youngsters have joined the business ownership ranks in recent years.

The Internet has certainly made it easier for many kids to carve out a business niche, and Sydney is a prime example. Her books are sold only online at http://www.cookiedalmatian.com/ , for $12 each, or 2 for $20.

The Web site has a dose of quirkiness that befits a preteen. Included are links to Dalmatian breeders and sellers, and fun facts about Cookie — who likes to eat steak and mashed potatoes and watch “Saturday Night Live.”

Though she loves dogs, Sydney doesn’t own a Dalmatian … yet. But she certainly knows plenty about them.

“It’s my favorite dog,” she said.

The youngster picked up the entrepreneurial bug at an early age. Two of her role models were the Olsen twins, Mary-Kate and Ashley. When she was 9, she came up with an idea for a theme restaurant based on television cartoon characters.

Though that idea didn’t get off the ground, she soon hatched her book plan with the help of her father, Marc Kramer, a marketer and business book author who has launched several businesses of his own.

“Sydney told me she wanted to start her own mystery book publishing business,” her father said. He agreed to help, partly because “children, especially girls, need activities that can build their self-confidence. Sydney isn’t a great athlete or a star student, but she is a very hard worker.”

As his daughter dictated, he typed — and challenged her to develop her story plots. The first book blossomed in just under a month, and includes black and white illustrations so her grade school audience can color in the characters. The father-daughter team followed the same formula on the second book started last summer.

While Marc Kramer has handled publishing, publicity, Web site development and financial underwriting details, some of the business basics have rubbed off on his daughter. She understands marketing and pricing, her father said. It was her idea, for example, to package both books for $20. The concept of a business plan, however, has been harder to grasp, though her father said she understands it is “much like writing down instructions for baking a cake.”

What hasn’t been lost on her has been a charitable touch. For each book sold, she donates $1 to a charity organized by her book illustrator. The youngster also wants to direct future proceeds to a shelter for abused women.

As for the bottom line, the $12 per book covers the printing and mailing costs — and leaves a profit for the author.

Sydney is certainly a big-picture thinker. She wants to try her hand at a longer novel by the time she turns 13 in September. After that? Perhaps a writing career. Who knows, Sydney Kramer could be tomorrow’s J.K. Rowling.