This article is published in the March 2010 issue.

Engaging Introductory Computer Science Undergraduates through Peer-Led Team Learning


As technology becomes ever more pervasive in everyday life and across many disciplines, one might expect that the study of Computer Science (CS) would become more appealing to more people, and to a broader spectrum of students. However, the number of undergraduate CS majors in 2009 is still much lower than it was during the dot-com boom of 2000, and the diversity of students majoring in CS has changed little over the same period, with about two-thirds of undergraduate CS students identified as white (according to the latest CRA Taulbee Survey). Over the longer term, gender diversity has even decreased—for instance, in 1985, 37% of CS degrees were earned by women, but 23 years later, the percentage was about half that (18% in 2008).

One effort to recruit and retain students, particularly under-represented students, in undergraduate introductory CS courses is Peer-Led Team Learning (PLTL). Since many students are not exposed to computer science in high school, introductory CS courses (hereafter referred to as CS1) are often a student’s first experience with CS. Large, lecture-based classes and complex one-person programming assignments can be daunting to students with no CS background. Since CS1 necessarily focuses on basic algorithmic concepts and programming, it may be difficult for students to appreciate the wide range of areas to which CS can be applied in real life, from network systems to machine translation. This article discusses how PLTL addresses the problems related to attracting students to the CS major, how PLTL has been implemented successfully at other universities, and our own experiences of building a PLTL program in the Computer Science Department at Columbia University.

The PLTL Paradigm

Peer-Led Team Learning supplements traditional science, technology, engineering and mathematics (STEM) courses in that students meet in small groups (6 to 8 people) facilitated by another student who has recently completed the course. The peer leader presents problems to the group, and then guides students as they collectively brainstorm, discuss and analyze the problems to come to a solution. The team-learning format encourages active learning, as opposed to the common paradigm of passively listening to lectures in an auditorium filled with hundreds of students. Using a trained peer leader allows students to participate more openly, without feeling ashamed for asking “stupid questions.” One Columbia student wrote that she liked having a peer leader because “a professor can be too intimidating.” Also, since the peer leader has just completed the course, she remembers what it was like to learn fundamental concepts from scratch, whereas these concepts are second nature to people who have been immersed in the field for years.

PLTL has long been applied successfully in other STEM disciplines—for instance, the PLTL Workshop Project at City College of New York has been using it in chemistry since the early 1990s. In CS, PLTL has been growing in popularity over the past five years due to the success of the Emerging Scholars Program in CS (ESP-CS) endeavor. Eight colleges and universities worked closely together to develop, implement, and evaluate a PLTL program for CS1 over three years. They have published detailed findings of their experiences and results (such as [Horwitz & Rodger 09]), as well as modules of course content, to assist other CS departments in starting similar PLTL programs.

In addition to using PLTL, ESP-CS uses targeted recruiting to attract students from under-represented groups. Students who may otherwise be turned off by the stereotype of computer scientists as lone programmers can discover through PLTL that CS is a collaborative discipline and encompasses much more than just coding. Initial studies have shown that students, particularly students from under-represented groups, are much more likely to be drawn to STEM subjects when the material focuses on teamwork rather than on working alone. ESP at Columbia University On the heels of the successful “PLTL in CS Workshop” at Duke University in 2007, the CS Department at Columbia University funded an ESP pilot program in spring 2008 to encourage more women to pursue CS beyond the introductory level and into the major. At Columbia, the CS1 course (COMS1004) is a large, lecture-style class with 150 to 200 students.

About 40% are women—a much higher proportion than the CS department where in 2008 only 16% of majors were women. During the pilot program, Professor Adam Cannon, PhD students Christian Murphy and Kristen Parton, and peer leader Kim Manis worked closely to come up with engaging problems from a variety of CS disciplines, including natural language processing, information retrieval, and social networking. The pilot was very successful. In the exit survey, all six students said they would recommend ESP to a friend. One student wrote, “These workshops gave me a better perspective of what computer science is. I have learned that it is extremely useful and pertains to problems and issues that are in our daily lives.” (Note: student quotes are taken from anonymous surveys.)

Thanks to a generous seed grant from the National Center for Women & Information Technology (NCWIT) and Microsoft Research, we were able to expand ESP to two sections in fall 2008, and have continued to hone and expand the workshop content over the past two years. In total, 43 undergraduates have completed ESP as students, and 10 have been peer leaders and/or assistants. In fall 2009, in preparation for expanding to even more students, we had one co-ed section and one women-only section. An important aspect of ESP at Columbia is networking—meeting other students who are interested in CS. This is particularly important because many advanced courses require working in groups, and networking is crucial for finding out about internships and other opportunities. To that end, ESP hosts an ice cream social each semester for all current and previous ESP students. “It was extremely rewarding to participate in something in which I not only found academic value but also social and recreational value,” said one ESP student.

ESP Topics

At Columbia, we chose to focus workshop content on algorithmic thinking, since students do a great deal of programming in COMS 1004. One student preferred not to program in ESP because it taught her that “much is done before programming begins” like “simply thinking about how to solve the problems.” Another agreed that the “thinking aspect [of CS] can get forgotten, lost, trampled over or almost done away with when programming.” Since ESP is only open to a subset of students in COMS 1004, we felt it was unfair to have the workshops tied directly to topics studied in COMS1004. Instead, we tried to demonstrate the breadth and variety of fields within CS. The ESP workshop topics we developed include: designing algorithms, encoding and encryption, machine translation, human-computer interaction, social network analysis, and hard (NP-complete) problems. As in many other universities, students at Columbia must complete a number of required foundation courses before they can take advanced courses. Unfortunately, this means that students may not get exposed to different areas of CS until their junior or senior years. If a student finds she is passionate about something early on, it can give her extra motivation to get through the requirements. As one student wrote, “[ESP] provided a bright future for some dark moments in class.”

PLTL Benefits

Perhaps not surprisingly, there is strong evidence that students who participate in ESP earn better grades than other students in CS1. The ESP-CS evaluation from other universities demonstrated that more than 80% of ESP students earned grades of B or better, compared to 68% for students who did not participate in the program; the results were even better when considering only the targeted groups, specifically women and under-represented ethnic minorities. The students who benefit most from ESP tend to be the peer leaders. The program provides tremendous opportunities for them to gain leadership experience and to build confidence in themselves as computer scientists and educators. Of the five students who have been ESP peer leaders at Columbia, one is currently a software engineer at Microsoft, and two others have used ESP as a stepping stone to further involvement in CS, participating in CRA-W Distributed Research Experiences for Undergraduates programs at top-tier research schools.


Thinking about starting a PLTL program in your department? Websites and provide excellent material on PLTL in general as well as CS content.

Kristen Parton and Christian Murphy are PhD students in the Computer Science Department at Columbia University.


[1] Horwitz, S. and Rodger, S., Using Peer-Led Team Learning to Increase Participation and Success of

Under-represented Groups in Introductory Computer Science. Fortieth ACM Technical Symposium on Computer Science Education (SIGCSE 2009).

Engaging Introductory Computer Science Undergraduates through Peer-Led Team Learning