For the first time in 40 years, Princeton University will not raise its tuition, the school announced Sunday.

Strong endowment returns, substantial alumni giving and changes in endowment spending rules have enabled Princeton to hold tuition steady at $33,000 for the 2007-’08 academic year, administrators said in a press release. Room and board will rise to $10,980 for an overall fee increase of 4.2 percent.

Last year’s 5 percent fee increase at Yale was not announced until late March. Yale administrators could not be reached for comment Sunday night.

Princeton’s $13 billion endowment yielded a 19.5 percent return on its investments in the 2005-’06 fiscal year. Yale’s endowment grew 22.9 percent in the same period. Princeton’s endowment is the largest in the Ivy League on a per-student basis, according to 2005 data from the Chronicle of Higher Education.

Despite holding tuition at 2006-’07 rates, Princeton should see more tuition revenue next year, as the Class of 2011 is expected to include 30 more students than the Class of 2010 as part of the university’s plan to increase the undergraduate student body from 4,700 to 5,200 by fall 2012.

Though he could not be reached for comment Sunday night, Yale Deputy Provost Charles Long has previously pointed out that Yale’s tuition is among the lowest in the Ivy League. The University has taken the lead among private universities in making college affordable, he said. Last year, Yale raised fees 5 percent while Princeton had a 4.9 percent increase. According to the College Board, average tuition and fees at four-year colleges and universities rose 5.9 percent between the 2005-’06 and 2006-’07 academic years.

Next year’s tuition was set as part of the 2007-’08 operating budget that was approved Sunday by Princeton’s Board of Trustees. The Yale Corporation will not approve the 2007 fiscal year operating budget until its April meeting, and the budget for the upcoming fiscal year, which begins July 1, will not be finalized until June, Deputy Provost for Undergraduate and Graduate Programs Lloyd Suttle said.