「三個臭皮匠勝過一個諸葛亮」或「三個和尚沒水喝」是團隊合作常產生的兩種截然不同結果。本研究將「多師入班」融入師資培育課程之中，以三位教師為一組的團隊形式，進入高中現場進行數學課後輔導；八週的過程中，鼓勵師資生循序漸進採取「六種合作教學」模式。本研究透過橫跨兩年的實務操作，訪談16位授課師資生與24位受輔學生，給予六種合作教學模式真實回饋，並且探討師資生同儕之間能否形成科勒效應的社會促進效果，增進教學實務與合作能力。研究結果認為合作教學能達到更佳的師生比例、關照學生差異、減少課堂干擾行為，提升中學生課堂參與，與數學領域課程綱要目標相互呼應。同時，師資生從過程中除了共同備課與議課外，更培養了「共教」的能力，此為現今師資培育課程中較為欠缺之一環，值得進一步加以推廣。

‘Two heads are better than one’ and ‘everybody’s business is nobody’s business’ are opposing perspectives on team collaboration. This research teamed up 3 pre-service mathematics teachers to deliver an eight-week after-school mathematics course. The’six co-teaching models’ were also adopted in their classroom practice. This article aims to investigate whether the incorporation of ‘multiple teachers practice’ and ‘co-teaching models’ in teacher education program can lead to Kohler’s effect of social facilitation and strengthen pre- service teachers’ abilities at teaching skills and team cooperation. Through interviews with 16 pre-service teachers and 24 senior high school students over a two-year implementation period, feedback about these models is gathered. It is concluded that co-teaching models could provide a better teacher-pupil ratio, attend to students’ personal differences and create more diverse learning activities, which echo the goals of the mathematics national curriculum. Apart from this, participating pre-service teachers are able to improve their ability at co-teaching. This collaborative skill in general teacher education courses has not gained enough attention, so is worth further emphasis in program design.