In this paper I explore the question of what counts as successful implementation of a mathematics professional development (PD) project at scale. Two kinds of upscale are presented and differentiated from one another: upscale of settings and upscale of values, and the link between this differentiation and how success may be defined is discussed. As part of the discussion, three models of taking a PD project to scale are described, namely replication, adaptation and reproduction, and these are tied to the degree of professional autonomy of teachers within the PD. The examination of these ideas draws on data from two PD projects for secondary mathematics teachers in Israel, that are now years after their pilot phase and still being implemented. The first project is aimed at supporting mathematics teachers in teaching mathematically at-risk students and in helping these students to succeed in high-stakes exams. The second project is aimed at enhancing mathematics teachers' reflection on their teaching practices, using classroom video as a tool. Both projects were implemented at scale across Israel, and reviewing results from these implementations enables some general insights to be gained regarding the success of scaled-up PD projects. The crucial role of PD facilitators in successful implementations is highlighted.

在本文中，我探索了一个问题，即大规模实施数学专业发展（PD）项目能否成功实施。提出了两种高档化，并且彼此区分：设置的高档化和值的高档化，并讨论了这种差异与如何定义成功之间的联系。作为讨论的一部分，描述了将PD项目按比例缩放的三种模型，即复制，适应和复制，这些模型与PD中教师的专业自治程度有关。对这些想法的研究借鉴了以色列中学数学教师两个PD项目的数据，这些项目距试点阶段已经数年，目前仍在实施中。第一个项目旨在支持数学老师教授处于数学风险中的学生，并帮助这些学生成功通过高风险考试。第二个项目旨在利用课堂视频作为工具，提高数学老师对教学实践的反思。这两个项目都是在以色列范围内大规模实施的，并且对这些实施的结果进行回顾可以使人们对扩大规模的PD项目的成功获得一些一般性的见识。着重强调了PD促进者在成功实施中的关键作用。并回顾这些实施的结果，可以得出有关扩大规模的PD项目成功的一些一般见解。着重强调了PD促进者在成功实施中的关键作用。并回顾这些实施的结果，可以得出有关扩大规模的PD项目成功的一些一般见解。着重强调了PD促进者在成功实施中的关键作用。