In another example, if a child is 11 or 12, the chances are he or she will be using a textbook called Mathematics: Applications and connections that teaches fractions by counting the sweets M&Ms, and asks how many hours a teenager would have to work at McDonald's to pay for a new pair of Nike shoes. The book, published by McGraw Hill, is used in 50 states and is officially endorsed by 15 of them.
Even more widespread is an in-school television station, Channel One, which is watched by eight million United States schoolchildren daily. The station provides 10 minutes of programming, including two minutes of compulsory advertising, as the price for free television and video equipment.
Its computer equivalent, a company called ZapMe!, provides free hardware but obliges schools to use its machines for four hours each day and expose children to adverts.
Advertising in US schools is reaching epidemic proportions. Some 150 schools and school districts have exclusive drinks contracts in what is rapidly turning into a turf war between Pepsi and Coca-Cola, neither of them noted for the nutritional or health values of their products. One Georgia teenager who wore a Pepsi shirt to his school's Coke Day last year was suspended for insubordination.
A backlash against this trend is beginning to take shape, however. The state of California has just passed a law banning product placement in school textbooks - dealing a severe blow to the fortunes of the McGraw Hill maths book, since California is the single largest education market in the country. New York, which bans exclusive Coca-Cola contracts, is considering a similar measure.
"We're ecstatic [about the California textbook ban] because it's an important precedent. It was a trend that was just starting," said Andrew Hagelshaw of the Center for Commercial-Free Public Education, a national non-profit campaign group. "If not checked, it would have expanded to other companies and other books."
But a second bill introduced in California recently, which would have banned classroom television and most other forms of advertising in schools, ran into a wall of resistance after Channel One hired a powerful lobbying firm.
The bill now sitting on the desk of the Governor, Gray Davis, for consideration is heavily watered down, merely mandating public hearings before schools can buy Channel One's services. According to Mr Hagelshaw, school districts rarely make their negotiations with private companies known to parents and teachers. San Jose had been talking to Pepsi for a year, but local papers only reported it days before the signing.
His group argues the deals are detrimental to schools even in financial terms, because taxpayers still pay for the time in which students are being bombarded by private advertising. Academic researchers recently calculated that Channel One costs US taxpayers $1.8bn a year.
"All these things are taking advantage of a captive audience. That's why companies want to get into schools," Mr Hagelshaw said. "But is it ethical for community leaders to buy and sell our students' attention? Are we going to treat our students as commodities we can barter in exchange for resources, or treat them as precious resources themselves?"