Dr. Sheldon Cooper, iconic condescending fussbudget, made sure he cleaned his hands with purifier after touching a snake in an episode of “The Big Bang Theory” a few months ago. It was a wholly forgettable few seconds of television, but proved the biggest ad-placement bonanza of 2011: More people interviewed by Nielsen could identify the brand of purifier he used, mostly because Dr. Cooper kept saying its name during his frantic search for the bottle.

Television alone has become a vast ad wasteland. We, the viewer, can no longer duck advertisements by hitting the clicker. If you watched every firstrun episode of “American Idol,” “The Biggest Loser,” “Celebrity Apprentice,” “Dancing with the Stars” and “The X Factor” in 2011, you were subjected to more than 2,200 productplacement ads — within the shows.

Nowhere is the battle for consumers more pitched than for the hearts of children. Advertisers spend billions each year to capture a child/tween/teen market that’s worth megabillions. Advertisers know young children possess the “pester factor,” willing to bug Mom and Dad to exhaustion to get what they want.

That battle is moving toward the classroom. With money running shorter each year, school districts are seeking new and creative ways to leverage extra dollars. Chelmsford ( Mass.) and Acton ( Mass.) have approved advertising policies. Westford’s policy allows ads, as long as they can’t be seen from inside the schools. Littleton has opened a discussion period on whether it should allow advertising, and where.

Advertising has been creeping into education for years. Some school districts subscribe to Channel One, which mixes current events and health tips with profiles on athletes and role models sponsored by the U.S. Army. BusRadio beams music to school buses, with an average of four minutes of advertising per hour.

Commercialism creep doesn’t stop there. Seven states now allow advertising on local school buses. Other districts are looking to sell ad spaces in hallways; one school district in Minnesota is paid $162 per 5-foot-by-10-foot ad spot, with ads covering both hallways and lockers. Other districts sell ads on report cards. While every little bit helps, branded items in the classroom take one more step down a slippery slope.

The American Academy of Pediatrics warns: “Research has shown that young children — younger than 8 years — are cognitively and psychologically defenseless against advertising. They do not understand the notion of intent to sell and frequently accept advertising claims at face value.”

In other words, educators who should be teaching critical-thinking skills will be unintentionally teaching blind faith in products.

Perhaps Alex Pratt, a Littleton (Mass.) High School senior, put it best at a recent meeting: Every day a person sees about 1,000 ads already. Pratt’s suggestions have merit: no political ads; allow ads from nonprofit agencies only; allow for-profit ads but only for healthy items; restrict ads to websites and newsletters.

The temptation to bring in extra revenue is great, especially if it means improving current standards and bringing in state-of-the-art technology. Yet children also need time to think, and to learn how to think, without intrusion.

— The Sun of Lowell (Mass.)