Sierra Magazine has released its annual “Cool Schools” environmental rankings of U.S. colleges and universities. Their rating appears to be just that—an assessment of the school’s green hip factor. At least, that’s what I’m left to guess. The magazine based its ratings on questionnaires sent to the schools and doesn’t disclose many details about how it evaluated the answers.

A comparison of the top 10 rankings from all three years Sierra has ranked these institutions shows the ratings aren’t consistent, either. Only two—Middlebury and Oberlin—made the top 10 all three years. Yale, a model of sustainability, has never hit the top of the list (it’s #14 this year). And Warren Wilson, a school that lives and breathes environmentalism, ranked #3 in 2007 but dropped to #18 this year.

As a result, it’s not very credible, even though the Sierra Club is a highly respected organization. (Full disclosure: I’m a member.)

Part of this can be explained by the explosion of schools that are making sustainability a priority. There are simply lots more colleges and universities making green claims. Now more than ever, those that communicate best about their programs—providing full information, with clear measures of success—will get the recognition.

I’ve found that educational institutions are uncomfortable about trumpeting their work generally and about marketing in particular. But they shouldn’t be. There’s a lot at stake. Both parents and prospective students care a lot about whether a school is green, with two-thirds of them saying the it would influence their decision to apply or attend, according to Princeton Review’s 2009 “College Hopes and Worries” survey.

Underwriters Laboratory’s UL Environment, which is certifying green products and verifying green product claims, has just announced the first product to be rated: Serious Materials’ EcoRock drywall. The product appears genuine, based on the excellent information on the company website, and it’s also got Cradle to Cradle certification.

While the UL assessment has UL’s brand clout behind it, they could add assurance and help alleviate consumer confusion over what’s truly friendly for the environment by providing complete disclosure about what their certifications mean on their website. Right now, there’s nothing on the UL Environment website that makes the label credible (except for the aforementioned brand power). By comparison, the Cradle to Cradle site has full disclosure.

Some questions they can answer: How and what are they testing? What is the process? What are the benchmarks and standards? Are they only looking at claims made or are they also comparing the product to similar ones? Do they consider what’s possible, so that if a company is only doing the bare minimum, it counts less?

Eco-labels are proliferating at a pretty fast clip. If they’re going to clear up confusion and help consumers sort out conflicting environmental claims and know what makes one thing greener than another, certifiers (and product marketers) need to help educate.

For more on the UL rollout, see Sustainable Industries’ excellent article. It was also covered at GreenBiz.com.

People trying to turn an innovative sustainability technology into a market-leading product or service often develop a religious fervor: theirs is the one true path to salvation. And that spirit can be great for maintaining organizational morale and motivating everyone to forge ahead through tough times. But it’s bad marketing.

Our sustainability challenges are enormous and fast-moving, and the reality is, there’s probably not a single solution to any one of them. When you say you have a silver bullet—the one thing that’s going to solve all our problems—you’re more likely to raise suspicions than inspire converts. Why? “I have the one best way” is an impossible claim to prove (at least until you’ve realized your dream), and it invites skeptics to pick your solution apart. Besides, we’ve all heard these boasts from others whose solutions didn’t pan out (or haven’t yet).

Maintaining credibility with outside audiences may require disciplining your enthusiasm a bit. “Over deliver and under promise” is still good advice, and it keeps the luster on your reputation.