A study in two El Paso (Texas) elementary school two-way bilingual education programs investigated factors in learning through first and second language, analyzed teacher development in a context of complex change, and identified promising school structures for collaborative professional development for these teachers. Of the 24 participating teachers, 12 from each school, half were bilingual (Spanish-English) and half were English monolingual. Classes were team-taught. All were observed monthly by trained observers; six of them were observed all day for an entire week. All were videotaped for an hour at randomly-selected times, and observed once a month during professional development sessions. Teachers also responded to an essay-type questionnaire asking them to elaborate on their teaching practices, team-teaching experiences, and overall problems and successes. Teachers all commented that the team teaching situation, with one monolingual and one bilingual teacher, offered new opportunities for personal and professional growth. Structures for the teams' development provided opportunities to learn collaboratively, including role-playing, peer coaching, classroom ethnography, and curriculum writing. The locally-constructed professional development program was found to be an effective structure for needed change. (MSE)