A Child Development Associate (CDA) training project director in north New Jersey initiated a practicum to create in-service training conditions and supervisory teacher attitudes that supported the teaching efforts of assistant teachers who were working toward CDA certification in a college-based program. Specific goals of the 3-month intervention were to develop strategies to involve cooperating group teachers in the in-service training effort. A collaborative training approach expanded the involvement of teacher trainers and all classroom practitioners. Strategies included: (1) selecting cooperating teachers who had previously gone through a similar training program; (2) distributing a detailed information packet to all cooperating teachers prior to the training; (3) conducting three meetings for cooperating teachers that detailed aspects of the training process; (4) instituting a three-way feedback conference in the field following classroom observations; and (5) developing a pilot "training of trainers" model for supervisors working in similar situations. Evaluation data indicated that the intervention was effective. All participants reported increased collaboration. A high percentage of trainees were successfully assessed in a shorter time period than before. Related materials are appended. (RH)