Digital darlings like Apple, Google, and Facebook have one more thing to brag about: high marks from a new Greenpeace report about clean energy. But on the other end of the spectrum, Amazon and Twitter flunked big time.

The report — “Your Online World: #ClickClean or Dirty?” — grades some of the web’s biggest sites on four metrics: transparency, policy, energy efficiency, and green advocacy. Amazon and Twitter each got three F’s and one D (see ya in summer school, suckers). Everyone’s fave microblogging site earned these harsh words from Greenpeace:

Twitter remains at the bottom of the industry for energy transparency, disclosing no information about its energy footprint. Twitter lags behind its competitor in social media, Facebook, which took significant steps to increase transparency and increase its use of clean energy soon after it went public.

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Greenpeace

ZING. And Amazon Web Services (AWS) — which owns your buddies Netflix, Pinterest, and Spotify — got major shade:

AWS has dropped further and further behind its competitors in building an internet that runs on renewable sources of energy, estimated at only 15%, and is the least transparent of any company we evaluated.

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Greenpeace

Somebody’s got a dirty (energy) secret! Too bad those bloodhounds at Greenpeace sniffed it out. On a more positive note, Greenpeace’s golden children weren’t always so green, so there’s hope. Writes Wired:

Facebook, Apple, and Google … [have] all made a serious effort to make sure that the energy that they use to run their data centers comes from renewable sources. For example, the three companies have pushed North Carolina’s Duke Energy to give them ways to offset their dirty energy usage by purchasing clean power from outside the state.

Maybe take a peek at their homework, Twitter and Amazon? Otherwise we’ll see you after class.