This paper presents an experience report of the design and implementation of a new introductory computer science curriculum for middle school piloted by ten teachers in the 2021–2022 academic year. This novel computer science curriculum is founded on the principles of functional programming, but also teaches imperative and event-based paradigms. We are proudly functions-first, using abstraction, domain and range, functional decomposition, immutable data, and powerful higher-order functions such as map, keep, and combine. We believe starting with functions teaches students the habit of solving problems functionally when possible, helping to avoid bugs in later programming experiences.

The curriculum uses the Snap! blocks-based programming environment, which brings the expressive power of a general purpose programming language, without requiring mastery of the syntax of a text-based language [16 ]. We take advantage of new Snap! features to develop “microworlds”: customized projects that simplify the blocks palette to further lower the cognitive load. We designed projects that use the multimedia features of the Snap! programming interface to explore data science, encryption, computational media, and graphics. We end with physical computing using the pocket-sized BBC micro:bit that students program using MicroBlocks, which is similar to Snap!, allowing for a seamless transition.

This paper describes our curriculum, reflects on the benefits and trade-offs of our design, and presents results from the experiences of our pilot teachers.