The Cristol Chemistry Building at the University of Colorado is a hive of activity on weekday mornings. Every hour, hundreds of laptop-toting students file in and out of its theater-style lecture halls, where classes are scheduled back to back.
In all, there are 33 courses at Colorado with 400 students or more. Three have more than 1,200. Most are broken into sections, but even those may have hundreds of students. One chemistry course is so big that the only place on campus where everyone can take the final exam at once is the Coors Event Center, Colorado's basketball arena.
Such arrangements are here to stay on US campuses.
There are already 18 million American college students, and that number is expected to increase by 2 million over the next eight years, as the value of a college degree continues to climb.
To get everyone through their coursework, monstrous class sizes are unavoidable.
That does not have to be a bad thing. At their best, giant classes can be effective and inspiring -- a way to get the best teachers in front of the most students.
But according to Carl Wieman, who won the 2001 Nobel Prize as a physicist at Colorado, such successes are rare.
Students often tune out and are turned off. Charismatic lecturers get good reviews but, the data show, are no more effective than others at making the most important concepts stick.
Most remarkably, when it comes to teaching not just "facts" but conveying to students the scientific approach to problem-solving, research shows that students end up thinking less like professionals after completing these classes than when they started.
"In a very real way, you're doing damage with these courses," Wieman, now a leading voice for reform, said in a recent interview.
Why are so many big classes broken?
One reason is faculty and departments closely guard their absolute power over teaching, and there is no central body in the US or even on campus to direct reform.
Many reforms also take money. If there were enough money, big classes wouldn't exist in the first place.
But state and federal policymakers are clamoring for more accountability and better graduation rates, and if faculty don't step up, bureaucrats might. Big classes are the obvious place to focus. The National Center for Academic Transformation, or NCAT, estimates that the 25 most common college courses -- in subjects like economics, English, psychology and the sciences -- account for 35 percent of four-year college enrollment nationally. That means a lot of people are taking a relative handful of courses.
Colorado, with a long tradition on innovative science teaching, is one of a number of campuses making significant changes in how at least some large introductory courses are taught and organized. Others include Maryland, MIT, Virginia Tech, Clemson and the University of Alabama.
The reforms go beyond simply reducing class sizes or encouraging lecturers to speak with more animation, though that's an element. Details vary, but one theme is a shift from a passive model of absorbing a lecturer's words to a more active one where lecturers guide and measure, but students learn the material more independently.
It's not necessarily popular with students, but the cognitive research says it is the way to make learning stick.
"In a traditional course the faculty are doing all the work and the students are watching," said Carol Twigg, president and CEO of NCAT, which is working with hundreds of universities to improve giant courses. "In a redesigned course, students are doing the work and faculty are stepping in as needed."