A teacher may say, "I have twenty years of experience," but just what does it mean? This study suggests explanations for the meaning of "Experience," not by looking at the number of years in a classroom, but at what teachers did in those years that could make the teaching experience equivalent to years of personal growth and development. Three Middle Level Science teachers' experiences were observed over two separate units of instruction. Teachers were engaged in conversations before, during and after every observation, such that their talk gave meaning to teaching. The teachers, early in their units, experienced tensions (stresses and anxieties) that affected their planning and implementation of teaching. The study determined that the teachers' learning experiences and personal growth were directly related to how they met the challenge of tensions. One teacher with very little science knowledge met the challenge of tensions in teaching by integrating her new science knowledge with her English and History knowledge and repertoire. She developed new practices that increased her energy and confidence in such a way that became self-sustaining experiences and growth. Two other teachers, despite science backgrounds, were less successful in meeting the challenge of tensions in teaching. Each found that the contents of the selected units required study and preparation, yet the teachers acquired information rather than truly learning the new subject matter. These teachers, in meeting the tensions of teaching, felt their energies wane, which reduced their dedication and effectiveness. As a result, neither teacher experienced personal growth. The negative experiences resulted in each teacher becoming more entrenched in a lecture mode of teaching to escape the tensions that existed. Learning new subject matter can produce tensions leading to experiences which affect teaching and potential for teacher growth. Incremental amounts of growth are possible, but only if a teacher responds positively to and meets the challenge of tensions in teaching, minute by minute, class by class. / Graduation date: 2003