This study is aimed at investigating students' annotation behaviors and their effects on learning achievement with pre-reading (reading before class) exercises and Web-based sharing mechanisms. An 8-week quasi-experiment was conducted with 125 sixth-grade elementary school students. The study shows the following results. First, a significant correlation was evident between pre-reading with a Web-based annotation tool and learning achievement. Furthermore, implementing a pre-reading sharing mechanism with Web-based annotation capabilities could stimulate and help students perform more useful pre-reading by reviewing others' annotations, thereby enlarging the effectiveness of pre-reading as it relates to learning. Second, participants' pre-reading exercises with a Web-based annotation tool revealed their preparation before class as well as reflected their prior knowledge, thereby helping the instructor to prepare the lecture well in advance. In the future, more advanced mechanisms, such as self-regulation learning, will be studied to encourage students to efficiently manage learning before class. (Contains 5 tables and 4 figures.)