In tandem learning, a model for two-way language learning originally developed for non-formal education, language is learned through interaction between two native speakers with different first languages learning each other's languages in cooperation. A high level of authentic learning characterises this model. The original tandem learning model has been developed and transferred to a formal educational context. However, the effects of this transition on the authentic character of tandem learning has not been investigated, and research in this field is needed. This paper aims to increase knowledge and understanding of the challenges of implementing authenticity of tandem learning in formal language education by analysing the learning tasks in a handbook developed for classroom tandem, a model for language learning and teaching, within second national language education in Finland. The results indicate a large variation in authenticity levels among classroom tandem tasks, indicating that the implementation of tandem learning in a formal educational context has compromised authenticity. The results identify aspects of learning tasks that are problematic and could be further developed. The results point to areas for further development of the classroom tandem model.