This article examines the effect of voluntary workshops on students' performance in a university for algebra-based introductory physics on the topics of electricity, magnetism and related areas. A workshop is an optional one-hour-per-week session that promotes a small group's peer instruction and co-operative learning, in order to enhance the conceptual understanding of physical principles and to improve problem-solving skills. During the workshops, a small group of students were encouraged to exchange ideas in a co-operative learning environment. Most students enrolled were poorly motivated, underprepared, and did not possess the prerequisite mathematics needed. For those who attended workshops, the result of scores on a standardized conceptual survey in electricity and magnetism showed a pre-test?post-test gain of 21% in the number of correct responses. This is to be contrasted with a 5% increase for those students who did not attend workshops. Further, we present a breakdown of the final letter grades obtained by students who attended workshops versus those who did not. Since the introduction of the workshops (out of 374 students), 95% of those who attended made a 'C' or better in the course. This compares to only 50% of the students who did not attend workshops and making a 'C' or better. The workshops have been offered since the Fall of 2010, but analyzed data includes fourteen years of student letter grades from 2001 to 2014 in order to study the effects on the workshops of the D, F, or W grades (DFW rate). We report a 7% reduction of the DFW rates, which we attribute to the incorporation of the workshops. The workshops are easy to implement and relatively inexpensive, yet appear to be an effective instructional method that enhances the success of underprepared students.