Updated at 5 p.m. with reaction from Bates College.

The U.S. Education Department ventured into the college rankings business Thursday, unveiling a public Web site that lists the most and least expensive colleges and those with the steepest tuition hikes.

A student at St. Mary's College of Maryland, the nation’s fourth-most-expensive public college. Photo by James A. Parcell/For The Washington Post (FREELANCE)

Mandated by federal law, the new lists are part of a federal push to reveal the true costs of college. College sticker prices are no longer a reliable measure of what the average student will pay, because of the proliferation of tuition discounting and the growing disparity between list price and “net” price. Aid is rising faster than tuition; published tuitions are climbing, but the net price of college for the average family is essentially flat. For families that don’t qualify for aid, of course, college costs are higher than ever.

Colleges will also be required by law to publish net price calculators on their Web sites by fall. Many already have.

The new federal lists of most and least costly colleges will look familiar to those who have perused the many previous lists in this vein, published by college ranking publications.

Bates College in Maine has the dubious distinction of ranking first in the nation among private colleges in 2009-10 tuition, at $51,300. Bates officials note that the figure is actually somewhat exaggerated, because the school’s annual fee includes living expenses. If Bates charged tuition separate from those expenses, it would not rank as the nation’s most expensive school.

“And therein lies another story, in that this particular list has an important apples-and-oranges aspect, inviting readers to compare comprehensive fees to tuition and fees only, with only an asterisk to note the significant difference between those two bases of comparison,” said Roland Adams, spokesman for the college. “Bates’ comprehensive fee is a statement of our total charges, and if all the schools listed were required to present that, there would undoubtedly be quite a different order of ranking overall.”

George Washington University is the top local representative on that list, ranked eighth, with tuition of $41,655.

(I should hasten to add that GWU, too, has a legitimate objection to such rankings because of its unusual policy of charging students the same tuition throughout their college careers. When the class of 2013 reaches senior year, they will still be paying $41,655, and their peers at dozens other schools will be paying more.)

Wells College in New York ranks first in the nation for one-year tuition increase, thanks to a 67-percent hike that reset its 2009-10 tuition at $29,680 — a figure that still puts the school well down the list of most expensive colleges.

Several art academies top the list of colleges with the highest “net price,” after subtracting grant aid, presumably because of the cost of art supplies.

It’s interesting to note the large national universities with unusually high net prices, including New York University, Northeastern University in Boston and Catholic University in Washington. High net price means the schools give less grant aid than their peers, which, in turn, signifies that they have smaller endowments than some of their peers and, thus, smaller aid budgets.

Penn State ranks as the most expensive public university, with annual in-state tuition of $14,416. St. Mary’s College of Maryland is fourth on the list, at $13,234.

In a recent interview, St. Mary’s President Joseph Urgo explained that the school’s tuition has been allowed to creep up to support its unusual mission as a public liberal arts college, endeavoring to compete with private liberal arts schools that boast small student-faculty ratios.

Many California universities appear on the list of public institutions with the largest one-year tuition increases: most or all of the Cal State schools saw tuition rise about 40 percent in a single year.