The purpose of this study is to provide effective strategies and suggestions of models for self-study tools suitable to fifth and sixth graders, by leading fifth and sixth grade students to establish hierarchal polycalve and dichotomous plant keys through observation, description, comparison, and synthesis in the activity-based courses of observation and classification of plant leaves, and by analyzing children¡¦s level of form cognition and capability of classification via children¡¦s observation records, the taxonomy model, and the contents of keys. In addition, this study aimed to realize students¡¦ learning difficulties regarding plants through their work, comments, interviews and the quantitative data. Also, by means of the reforms to relevant teaching methods and teaching material, this study showed how students could have a better learning experience with plants. Based on the quantitative and qualitative data, the major findings of this study are summarized as follows: 1. Observation capability: The tactile sense was the important medium by which primary school students explore the world, with leaf texture in the highest observational record. Visually, students had better observation capabilities for characteristics of larger-scale forms. 2. Classification model: The standards that students most commonly used were ¡§color,¡¨ ¡§vein,¡¨ ¡§margin,¡¨ and ¡§shape.¡¨ The results of classification were more consistent with the last three standards, and the results of classification in groups were especially similar when proper morphological terms were used to express classified items. It was thus clear that morphological terminology can help students to classify plants. 3. Plant key: When devising the plant key suited to primary school students, it was better to use the polyclave method in one searching stage to show different characteristics in the same region, and to use the dichotomous method to show similar characteristics that are difficult to distinguish. When expressing options using clip art and proper terms simultaneously, students exhibited the best comprehension. 4. Studying attitude According to the quantitative data, activity-based courses only raised students¡¦ learning interest a little. However, interviews and sharing of study experiences revealed that learning by doing can improve their observational capabilities and learning memories. In addition, students would be more concerned for the relationship between human beings and the environment.