After three straight years of receiving a B+, Yale improved its mark for its sustainability efforts.

In a report released Wednesday, the Sustainable Endowments Institute awarded the University an A- in its 2010 College Sustainability Report Card. The survey tracks the colleges and universities with the 300 largest endowments in the United States and Canada. Yale tied with 25 schools, including Harvard and Stanford; no schools received an A this year.

The Sustainable Endowments Institute, a nonprofit advocacy group based in Cambridge, Mass., criticized the University for not disclosing how it invests its $16.3 billion endowment. “Endowment Transparency” was the only one of nine categories in which Yale received a grade lower than an A; it received a D.

The Yale Investments Office discloses holdings to Yale trustees and senior administrators but not to the general public.

“This is the most challenging category for most schools because it’s a big shift in practice and thinking,” said Lisa Chase, a senior communications fellow at the Sustainable Endowments Institute. “If the public has access to how money is invested, it will be managed socially and environmentally responsibly.”

Students have periodically raised concerns about the way Yale’s funds are invested. In November 2008, about 20 students from the Undergraduate Organizing Committee led a four-hour sit-in in the Yale Investments Office to protest working conditions at the HEI Hotels and Resorts, in which they claimed Yale had a stake.

Nothing came out of the students’ efforts.

“Money speaks,” said Erica Rothman ’12, a Student Taskforce for Environmental Partnership coordinator. “It’s hard to be truly sustainable if you’re investing in coal or deforestation, for example. It would counter everything we students are doing, because it has a far greater impact.”

Despite the lack of transparency, she said, the University has taken concrete steps towards sustainability. By 2020, the University aims to reduce greenhouse gas emissions to 43 percent below 2005 levels. It spends 35 percent of its food budget on local and organic products.

The Sustainable Endowments Institute was founded in 2005.

Correction: October 11, 2009

A previous version of this story misstated the title of Lisa Chase, a senior communications fellow at the Sustainable Endowments Institute.