Reading science has reached consensus that background knowledge is essential for reading comprehension. What remains an open question for the science of reading, however, is how and when this background knowledge ought to be developed. Teachers often include activities meant to activate background knowledge immediately prior to read-alouds. However, these activities also often provide completely new knowledge, the efficacy of which has not been well studied. The goal of the current study was to examine differences in narrative comprehension when background knowledge is activated before reading (i.e., students are reminded of things they already know) versus provided before reading (i.e., students are informed of new information). To that end, 92 participants were tested on familiar information (i.e., activated knowledge), taught novel but relevant information (i.e., provided knowledge), or taught novel but irrelevant information (i.e., neither activated nor provided knowledge) prior to reading a story. Regression analyses showed that whereas students showed basic comprehension no matter when they learned the information, attention and more advanced comprehension skills were more successful when students already knew about a topic and merely had their knowledge activated. This suggests that common prereading activities may not be successful for students who are unfamiliar with the topic. Reading science must continue to explore how to develop this crucial background knowledge.