A Newsletter of the Center for Teaching Effectiveness
Spring 1996

But I Teach a Large Class...

Linda Dion,

I have taught hundreds of students Introductory Biology over the span of many years. Ihad finally achieved that comfortable security of having a ready-made set of lecture notes, volumes of exam questions banked away, pre-printed study guides, practice exams, and quizzes, and a sense of predictability regarding the course.

Strangely enough, I was also bored and bothered. Bored from lecturing about the same things year after year, and bothered because my lectures came across so dogmatically that I was failing to impart to the students the uncertainty of scientific inquiry and the satisfaction of finding solutions to problems. The fact that I was "in charge" of the course had been construed by my students (with my help) to mean that I was the "possessor of knowledge," the sole provider of information, and that they were the "cups to be filled to overflowing." The structure of the class prevented students from seeing that all this information in textbooks and in my lectures had been preceded by years of research and ongoing questioning. They did not see that I, the presumed "authority," was a learner also. Clearly a change for my course was in order. I wondered if engaging my students in a more cooperative learning endeavor might empower them to take a more active role in their survey of biology, and might, at the same time, infuse me with renewed excitement about the course.

A conference on Problem-Based Learning offered by the Center for Teaching Effectiveness (CTE) at the University of Delaware aptly coincided with my restlessness and search for a solution. I learned techniques for writing real-life problems, ways to deal with group dynamics, and principles of transforming a traditional lecture course into a group-centered problem-based learning (PBL) course. I was interested in PBL, but could I successfully apply these techniques to my class of 80 students, who were mostly inexperienced first-semester freshmen of varying backgrounds and abilities? There was only one way to find out, and it made me suddenly more excited about teaching Introductory Biology than I had been in several years.

I am now approaching my fourth semester of using PBL in a large class and have accumulated some tips which may make the adventure smoother for someone who wishes to try the method. First, I began in an ordinary classroom (one not designed for group meetings), and without teaching assistants or tutors, thus I knew I would have to manage all groups on my own in a somewhat chaotic setting. Consequently, I decided to retain lectures for about 80% of the classes and use problem-based learning for the other 20%, limiting the PBL to in-class sessions, rather than out-of-class meetings. This would allow me to maintain the organization and the structure which I presumed were necessary for PBL to succeed with a large class.


The personal organization of the instructor (including what is communicated both verbally and non-verbally) and the organization of the classroom during a PBL session are paramount to the success of a large PBL class. Anyone who might be tempted to stroll semi-prepared into a lecture, knowing he/she can carry it through, should think twice about doing this for a PBL class. If you want students to endorse this process as sincerely as you do, and use their time as efficiently, you MUST, and I repeat, MUST, be thoroughly organized and prepared. This includes the following:
  1. Clearly define your purpose for doing PBL, the procedures you will use, and your expectations - do this BEFORE your first PBL session.
  2. Assign students to groups by an arbitrary method (such as alphabetically) and distribute the list of assignments to students the class period before the first PBL session. Four students per group is a good size. The list should show all groups, numbered, and all members of each group. (Note: Group assignments do not preclude the option of forming spontaneous groups of two or three for a quick simple question you decide to introduce during a lecture class -- this "Pair and Share" method with a neighbor eliminates the chaos incumbent with students locating their assigned groups.)
  3. Request a room conducive to group work. For 80 students, a room with tables is best, followed by a room with moveable chairs. (EditorŐs note: Pearson 101C seats 66 students at round tables.)
  4. On the day of your first PBL session, prior to student arrival, assign seating by pasting group numbers on all seats, if seats are not already numbered.
  5. Set up your room so that you are accessible to all groups. In a large lecture hall with fixed seating, this may mean leaving empty rows between group rows.
  6. Bring extra group lists, masking tape, stapler, extra textbook, reference materials, copies of problems for each group and for each group member.
  7. Anticipate problems and be ready to handle them swiftly.


More structure is needed to manage PBL in a large class than in a small class. The following methods are useful to convey to the class that this otherwise "chaotic" situation is well under control and has a definite purpose.
  1. Introduce a problem at the beginning of the class, or during the previous class, with a very brief "mini-lecture."
  2. If the problem is printed (rather than viewed), provide copies for each group and for each person in each group.
  3. Furnish printed questions related to the problem (with space provided for answers). Copies should be furnished to each group member and a copy to each group. The group's copy, signed by all participating members, should be turned in as the group product at the end of the period. If questions are not appropriate for the problem, then explain what product is expected as a result of the group work for that day.
  4. If a printed problem is written on more than one page, and solutions to the problem unravel with each new page, then give out the pages one at a time, requiring that answers to one page be turned in before the next is dispensed. Suspense is a great motivator.
  5. Assess progress at regular intervals. If necessary, interrupt group work to correct misconceptions, or to bring groups up to par with one another.
  6. Allow time for class discussion of the problem at the end of the PBL session, or at the beginning of the next class period.

In addition to the importance of organization and structure to the success of PBL in a large class, I found that the design of the problem, and the evaluation procedure had to be considered carefully also. Problems are best if kept short and reasonably simple. This does not imply that they cannot be challenging, but they should address what you consider to be the most important concepts for the course, rather than a complex factoid of knowlege which digresses from the essentials. If doing the problem within one class period, incorporate a challenging "bonus" question at the end which is open-ended -- this gives fast groups a challenge to work with while slow groups are finishing the required work. Designing a problem that can be addressed during class time, using the text as primary reference, keeps the groups in relative synchrony with one another, making it easier to monitor all 20 (or more) by yourself.

Your methods for evaluating work done through PBL sessions should be communicated clearly to the class at the beginning of the course. What percentage of the final grade will be from PBL? What type of group product will be expected from each problem session? Will individuals be graded as well as groups? Some suggestions:

  1. Require some type of group product (to be graded) from each PBL session. Grading 20 papers is much easier than grading 80.
  2. Grade participation as well as quality of group work.
  3. Occasionally require an individual product based on group work, such as a one-minute paper about an issue learned from a problem. This rewards students who were actively involved in group learning and discourages "free-loading."
  4. Use peer evaluations at the end of the term and possibly mid-term. This is especially helpful for judging the relative contributions of members in a large class, where it will be difficult for you to personally evaluate all individuals.
  5. Design exam questions which reflect the contents of a problem or the thinking process used for problem solving. If large classes necessitate multiple choice exams, then design such questions based on PBL topics, as well as on lecture topics.

In conclusion, using PBL in a large class requires attention to detail, organization, and some built-in structure which may not be necessary with a smaller class. The additional time involved for you, the instructor, pays off handsomely in the enhanced rapport which you establish as a co-learner with your students. Learning will become more of an active endeavor for students, rather than just for you, the instructor. Students will interact much more with one another than they would in a traditional lecture course, and a feeling of cooperation rather than competition should pervade the classroom. And you will never be bored - there are always new problems to research and write, and old problems to refine. New groups of students have ways of re-inventing solutions from new perspectives - your class will become a section of actively engaged creators-of-ideas rather than docile, passive recipients-of-knowledge.

Last updated Feb. 20, 1997.
Copyright Linda Dion, Univ. of Delaware, 1996.