Self-regulated learning (SRL), in which students monitor and adjust their learning, is considered particularly important for correspondence high school students who study independently. To accommodate diverse reasons for enrolling, such as employment or school refusal, correspondence high schools in Japan have introduced various attendance types. However, the effect of attendance types on learning strategies and outcomes remains under-examined. This study examined whether learning strategies, including SRL, varied across attendance types, using data from a survey of correspondence and full-time high school students, with a focus on correspondence students (n = 1,459). We also compared beliefs about learning and friendships, school adjustment, and academic achievement across attendance types. Students were enrolled in one of four attendance types: Online Learning (OL), home-based study with online instruction; Once-a-Month (1M), home-based study with monthly on-campus instruction; Once-a-Week (1W), weekly on-campus instruction; and Three- or Five-Day course (3-5D), face-to-face classes three or five days per week. One-way ANOVA revealed significant differences in instrumental friendship beliefs, cooperative learning strategies, peer adjustment, and academic achievement across attendance types. Instrumental friendship beliefs were higher among 1W students than among OL or 1M students. Collaborative learning strategies were highest among 3-5D students, and were higher among 1W than among 1M or OL students. Peer adjustment increased steadily from OL to 3-5D. Academic achievement was highest among 1M students, followed by 1W and 3-5D students; 3-5D students outperformed OL students. These findings suggest that frequent school attendance is associated with stronger peer relationships and higher academic achievement. Future research should investigate how beliefs and learning strategies affect school adjustment and achievement across attendance types, and how to provide opportunities for peer interaction effectively.