現有文獻指出在程度差異大班級中的英語教學相關研究傾向將研究重點置於教師遇到的困難以及他們發現可有效解決問題的教學實務方法。少有研究會進一步研究教師的心理層面以解釋這些教學實務方法是如何以及為何被使用在特定教學時機與場域，也因此使他們的研究討論僅流於教學的表層。 為了呈現一個對程度差異大班級中的英語教學較為全面且深入的理解，本研究採用教師敘事、訪談、觀察以及文件分析來研究一教師如何在程度差異大班級中教英語、她在這樣的班級中教英語時抱有什麼教學認知以及她如何發展出這樣的認知。 研究結果顯示此研究對象之教師持有四大教學認知與實務，包括（一）瞭解並同理其學生、（二）使其教學實務多樣化以容納學生的多樣性、（三）將學習標準層級化以照顧學生的多樣性，以及（四）接納有些事情乃是其力所不逮。經分析後，研究者發現這四大教學認知與實務乃是研究對象之教師基於她所持有的廣泛經驗，不論其發生於教室內或外，所進行省思後，構成並再次構成的教學認知與實務。然而，儘管懷有這四大教學認知，研究對象之教師並非總能落實符合其認知的教學實務。事實上，研究者發現研究對象之教師能實施符合其認知之教學實務的程度乃是她個人落實其教學認知的能力與外在教學場域願意提供多大空間予其落實其認知於實務之互動下的結果。 試圖促進在程度差異大班級中的英語教學與研究，本研究向在此種班級中的四大主要族群，包括教師、教師培育者、研究者以及此班級下的其他相關人士提出相關建議。 / A review showed that existing literature on teaching English in multilevel classrooms tends to focus on the difficulties teachers encounter and practices they find to be effective in addressing the problems in teaching such classes (Chen, 2009; Chiang, 2003; Liu, 2004; Maddalena, 2002; Xanthou & Pavlou, 2008). Few studies have probed further to investigate the mental dimension of teaching that accounts for how and why certain practices are adopted in particular periods of class time and specific teaching contexts (Lu, 2011; Teng, 2009), hence rendering the discussions rather superficial touching only the surface of teaching. To present a more holistic and in-depth understanding of teaching large multilevel English classes, the present study drew on a teacher narrative, interviews, observations and document analyses to investigate how the teacher participant taught large multilevel English classes, what cognitions she held in teaching such classes and how she developed such cognitions. The findings revealed that the teacher held four major cognitions and practices in teaching large multilevel English classes, including (1) knowing and empathizing with her students; (2) building variety into teaching practices to accommodate the diversity of students; (3) adding differentiation into criteria to attend to the diversity of students and (4) admitting that things can be beyond her control. The four major cognitions and practices were found to have structured and restructured through the reflection that the teacher undertook on the vast experiences that she had accumulated both inside and outside the classroom. However, despite holding these cognitions, the teacher could not always implemented practices that conformed to her cognitions. In fact, it was found that the extent to which the teacher could implement practices congruent with her cognitions was the interactive result of her internal capacity to find spaces to realize her cognitions and the surrounding teaching contexts’ willingness to allow room for her to put her cognitions into practices. In an attempt to facilitate instruction and research in large multilevel English classrooms, the study yielded implications for four parties working in the relevant contexts, including teachers, teacher educators, stakeholders of teaching contexts other than teachers, and researchers.