Literacy skills are pivotal for children to become schooled and educated and to engage with written texts in everyday life. Learning to read is a primary skill that children acquire at school. Supervised, supportive guided reading aloud may help children improve their reading skills. However, such a supportive context is usually difficult to realize at school since teachers do not have enough time to give directed individual feedback. An ASR-based reading tutor could be a solution in such a pressing situation, as such a tutor can 'listen' to children reading, provide individual feedback on errors, and store information on reading practice into logfiles.In this study, we investigated the effectiveness of an ASRbased Reading Tutor for Dutch first graders, in which different forms of feedback were implemented. We collected data from 525 first-graders in 44 schools, with 263 pupils who received explicit feedback and 262 pupils who received implicit feedback. Analyses based on mixed linear regression models indicate positive effects of both feedback forms on reading accuracy and a trade-off relationship between accuracy and speed.