Data management is central to many CS innovations: Smart home technologies and the Internet of Things, for example, are based on processing data with high velocity. One of the most interesting topics emphasizing several challenges in this field is real-time data analysis. In secondary CS education, it is only considered marginally. So far, there are no tools suitable for general-purpose real-time data analysis in school. In this paper, we discuss this topic from a secondary CS education perspective. Besides central concepts and differences to traditional data analysis using relational databases, we describe the development of a general-purpose \(\textsf {Snap}{\textit{!}}\) extension that allows accessing and processing data from various sources. Thereby, students are enabled to conduct data analyses using, for example, sensor data or web APIs. With the example of a weather station, we outline how this tool can be used in school for analyzing sensor data generated in the classroom.