I want to start by saying that yes, open spaces can be effective if the pedagogy aligns. Schools that have great success realize they are not intended for direct instruction and leadership and teachers shift pedagogy to focus on team-teaching and leverage the space to support multiple modalities and differentiated instruction. However, even when pedagogy and the space align, if the acoustics are not addressed, what could be an exciting, collaborative atmosphere with a healthy "buzz" of learning, can become a loud, ineffective space and up go the walls.
This is the scenario that happened at a local school in Melbourne. The school is divided into separate buildings operating as neighborhoods for each grade level. When built a few years ago, each neighborhood was nearly completely open aside from a few offices and building support spaces. However, acoustic treatments were non-existent. Imagine having 100+ students all working as separate classes with four educators in an open warehouse space. That was their reality. The noise was unbearable as the metal finishes and hard surfaces created an echo chamber of sound. Thus, after bearing through this for a couple of years, walls were added.
Depending on the type of walls constructed, this moment can be a dismal one. However, lucky for this school, their forward-thinking Principal understood why the space was open in the first place and the educational goals with which it could align. Thus, instead of popping up solid walls, he opted for glass walls and large, sliding doors. This allows for some level of connectivity as it's desired and keeps the visibility between learning groups at the forefront while keeping the acoustical issues in check.
Soon after my visit, I had a firsthand experience with acoustical issues in open spaces, ironically while listening to chat given by acoustical experts, Ecophon. We discovered later that this was a planned experiment. The organizers knew the space, which is intended to be a "teaching space", does not work well due to its close proximity to a student cafe, and lack of acoustical barriers. As the lecture went on, more and more of the audience asked the speaker to talk louder. The organizers finally made the call and moved the discussion to an acoustically separated classroom.
I would like to reiterate that this post is not against more open, informal spaces. Instead, I hope to instill the importance of alignment between the design of a space and how it is meant to be used. The "teaching space" should never have been deemed that. Instead, it can work great as a group study area for those like myself who enjoy a good amount of background noise. Similarly, open plan spaces are not meant to support four teachers lecturing to their individual classes. The most important point, however, is that even if this all aligns, acoustics are the make or break design decision that must be accounted for.