In this paper, we will present and discuss data from a research project called MIRACLE, in which high school students learned about energy and energy transformation in a technology-rich learning environment. This learning environment spanned across a classroom, a science center, and an online platform specially designed to support coherence across resources and concepts. During the project, the students tweeted about different aspects of energy and energy transformation. These tweets were based on facts gleaned from previous knowledge or on knowledge that they found relevant during their learning trajectory. This knowledge could be found, for example, in textbooks, on web pages, or on posters in the science center. The tweets were meant to support the students in collecting and creating knowledge content themselves and to gradually increase their understanding of the curricular topic. At the end of the project, the students were asked to write a newspaper article and were encouraged to use their tweets as a source. However, the findings show that the students turned to officially approved knowledge sources when they had to write their assignments. This finding adds to previous studies on college and university students. We discuss the possible reasons for this by examining the lack of established practices for using tweets in schools; more specifically, we discuss how this becomes particularly evident when activities are assessment-oriented. [The MIRACLE project was funded by the Research Council of Norway, grant number 201332.] [For the complete proceedings, see ED557171.]