The battle against high-priced tutors is heating up at Riverdale Country School.

Riverdale, like other private schools, has been hoping to crack down on the expensive tutoring some of its students seek by trying to convince parents that most children simply do not need it.

But when administrators at the school lashed out at one of the tutoring companies for using a class list to solicit clients, the company fired back, saying they would not be needed if the students did not have such crushing workloads.

On Friday, Kent Kildahl, Riverdale’s head of upper school, sent a letter to parents warning them about Brattle Street Coaching. (See the letter below.)

The company, whose cryptic Web site does not include names of its tutors, sent letters last week to the parents of juniors enrolled in “Constructing America,” a signature Riverdale class which has a reputation for being tough, promoting their business to help students in the course.

According to Mr. Kildahl, Brattle Street used the parent directory to do the mailing to juniors and their families, “a serious misuse of the directory and an abuse of both their privacy and the school itself.”

Mr. Kildahl said he understood he could not make the “tutoring-for-profit that Brattle Street typifies” go away, a fact that might relieve some of the parents who use such services. (Here is the way one parent summarized the experience of hiring $500-an-hour tutors for his kids: “I’m paying a half a million dollars for their education. Of course I’ll pay for tutors to make sure she has the grades and the scores to get into the college she wants to go to.”)

But Mr. Kildahl said the teachers and administration at Riverdale had worked hard to make the class manageable so that tutoring, at least for most children, should not be necessary.

“Please do not give into the seductions, based on scare tactics of firms like Brattle Street,” he said in the letter to parents. He also noted that the services being offered — summaries of the primary source readings, help with take-home assignments — are exactly what the students are supposed to be doing for themselves.

On Monday night, Leelila Strogov, founder of Brattle Street, said blaming her company was the wrong response.

“The blame from Riverdale is coming in the wrong direction,” she said in a telephone interview. “They should look in the mirror.”

Ms. Strogov compared the “Constructing America” course to torture.

“If there’s something we can do to help these children," she said, "we don’t see why we shouldn’t do that.”

Ms. Strogov, a graduate of the Massachusetts Institute of Technology, started tutoring other students in college and continued doing so on and off until she founded Brattle Street with her husband (M.I.T., Harvard Business School) in 2004.

She said she started tutoring Riverdale students enrolled in "Constructing America" in 2006, and that the company, which charges from $200 to $600 an hour, adopted a revised fee structure because of the number of hours students were logging with them (after the third hour, the fee is reduced by half).

“This is the only class that kids needed so many hours of tutoring," she said. "The fees were looking ridiculous.”

She defended the summaries that Brattle Street has written to help students.

“You are creating organizational materials from which they can learn. Nothing is wrong if you use it in addition, and not instead,” she said.

As for why she does not list the names of her tutors on her Web site, she said she did not want to immerse her employees in the controversy over tutoring. "I know a lot of people don’t look kindly on the tutoring business," she said. "Schools think it’s cheating, which is ridiculous.”

If the schools were teaching well, she added, tutoring would not be needed.

Dominic Randolph, Riverdale's head of school, and Mr. Kildahl issued this joint statement to SchoolBook in response to Ms. Strogov's comments:

"Constructing America," our 11th grade American Studies course, is an amazing intellectual experience for our students that we stand by completely; we believe it is unique in its interdisciplinary approach to American history and culture. Indeed, our students point to it consistently as one of the best parts of their high school experience. We wrote to our parents to express our regret that their privacy had been violated by marketers who misused our directory. We find the scaremongering and marketing techniques used by such tutoring companies disheartening, and the fact that they would prey on the fear that they themselves generate absurd.

In its original letter to parents, Riverdale said its lawyers would be reaching out to Brattle Street to “discuss the use of our directory.”

Ms. Strogov said that she understood why Riverdale was upset about the directory, though she said she obtained it legitimately: it was given to her by families with whom she works, she said. And she said she only reached out to the students in "Constructing America" through postal mail, not by telephone or e-mail.