This research investigated the impact of combining two approaches to inservice teacher education (action research and train the trainer) on teacher attitudes and practices. The inservice developed assessment approaches aligned with cooperative learning instructional approaches. Teachers were introduced to a model of collaborative assessment aimed at improving students' abilities to self-evaluate. A team of five university and school/district personnel conducted a series of three inservice sessions over 4 months. Teams of teachers from several schools were paired, with two teachers attending the first full-day inservice as trainers, working back at the school with their partners (trainees), then attending the second and third inservice sessions together. The effects of the inservice were measured in a pre-post design which examined the impact of the inservice design on personal teaching efficacy, general teaching efficacy, commitment to authentic practices, and commitment to traditional testing practices. Data were also collected on how teachers used the four stages in the study model for teaching self-evaluation. Researchers found significant pre-post changes. Use of self-evaluation procedures increased substantially, commitment to authentic assessment practices increased, commitment to traditional assessment practices declined, and personal teaching efficacy scores were higher. The action-research-enhanced train-the-trainer approach facilitated teachers' movement toward student assessment practices congruent with the ideals of the cooperative learning/teaching practices. This approach also succeeded in enhancing teachers' beliefs about their competence. (Contains 48 references.) (SM)