Teacher educators have focused on designing learning environments ‘for’ rather than ‘with’ teacher candidates. However, a co-design collaboration with teacher candidates has been recently suggested as a critical feature for effective teacher education programs. In this study, a co-design team, including preservice science teachers (PSTs) as co-participants of the iterative design process rather than research subjects, collaboratively developed formative assessment (FA) practices based on the approach of conjecture mapping in a chemistry laboratory setting. This study aimed to examine the role of PSTs as co-designers and their contributions to the progressive development of the most robust design of FA practices, drawing on relevant theoretical perspectives and considering the characteristics of a general chemistry laboratory environment. Sixteen PSTs participated in the study for a whole semester. This qualitative-interpretive study employed the following data sources: classroom observations, audio tape recordings of co-design meetings, and field notes. Results under four main themes showed that the PSTs as co-participants can actively engage in and effectively contribute to creating the FA design for their chemistry laboratory investigations. Using conjecture mapping as an approach for critical and reflective thinking on design elements, the PSTs could focus on their own thinking and that of others when making, testing, and revising co-design decisions based on the relevant theory work and empirical findings as the design principles for the FA-embedded laboratory practices. This study has important implications for the inclusion of teacher candidates as active co-designers of high-leverage instructional practices such as FA in science learning settings.

教师教育工作者专注于为教师候选人设计学习环境，而不是与教师候选人一起设计学习环境。然而，最近有人建议与教师候选人共同设计合作作为有效教师教育计划的一个关键特征。在这项研究中，一个联合设计团队，包括作为迭代设计过程共同参与者的职前科学教师（PST）而不是研究对象，在化学实验室中基于猜想图的方法合作开发了形成性评估（FA）实践环境。本研究旨在借鉴相关理论观点并考虑一般化学实验室环境的特征，探讨 PST 作为共同设计者的作用及其对 FA 实践最稳健设计的逐步发展的贡献。十六名 PST 参加了整个学期的研究。这项定性解释研究采用了以下数据源：课堂观察、协同设计会议的录音和现场笔记。四个主题下的结果表明，PST 作为共同参与者可以积极参与并有效地为其化学实验室研究创建 FA 设计做出贡献。使用猜想图作为对设计元素进行批判性和反思性思考的方法，PST 在根据设计的相关理论工作和实证结果制定、测试和修改协同设计决策时，可以专注于自己和他人的思考FA 嵌入式实验室实践的原则。这项研究对于将教师候选人纳入科学学习环境中的 FA 等高杠杆教学实践的积极共同设计者具有重要意义。