Background and Context: To offer more experiences in the field, our study employed secondary school pre-service teachers as assistants in courses for secondary school students learning computer coding with the help of smart textiles. Objective: Did pre-service teachers assisting in CS courses have more highly developed pedagogical content knowledge (PCK) and more positive attitudes toward computer science teaching than a control group. Method: We administered a teacher questionnaire (N = 47) with items related to pre-service teachers' awareness of CS and attitudes toward CS learning environments. Data on emotional experiences were collected. Findings: Two moderate effects helped to explain variances between the groups on measures of belief in effectiveness of CS learning and peer support over time. Their positive experiences were confirmed by their decline in negative emotions. Implications: The results of our research might help to expand our not yet very broad knowledge of meaningful educational experiences for pre-service teachers' CS education.