Children learn language through participating in language-rich activities such as book reading. This longitudinal qualitative study explored the perception of 11 teachers and 78 kindergartners regarding children's participation in book-reading in order to understand how it is experienced by those most involved in this activity. Each participant was interviewed three times, before, after and 3-month after a professional development program on interactive book reading. The reflexive thematic analysis yielded four themes describing: 1) the shift from a more adult-controlled to a more spontaneous child participation; 2) the challenges teachers faced in facilitating children's participation while maintaining the rhythm of the story; 3) the evolution of children's perceptions of their role in reading; and 4) children's perceptions of the relationship between their behavior and their right to participate. The findings have implications for supporting collaboration between teachers and school-based speech-language pathologists to facilitate the implementation of language-supportive practices in the classroom.