Self-regulated learning has a positive effect on academic outcomes; however, little is known about whether and how teachers at various education levels promote it in their classes. Video-based classroom observations were conducted to assess primary and secondary school mathematics teachers' direct and indirect promotion of self-regulated learning (SRL). Teachers' implicit and explicit instruction of SRL strategies (direct promotion of SRL) and the learning environment they created (indirect promotion of SRL) were rated according to how conducive they were to self-regulation. In addition, semi-structured interviews were conducted with the secondary school teachers to gain insight into their subjective views on SRL. Although the teachers' instructional practices could foster SRL, teachers spent little time explicitly teaching SRL strategies. Moreover, they taught mainly cognitive strategies and very few metacognitive strategies. These results were more pronounced at the primary level than at the secondary level. Primary school teachers provided learning environments conducive to self-regulation more often than secondary school teachers did. The interviews revealed that the teachers lacked knowledge about metacognition as an important component of SRL and were rather reluctant to promote it; however, most of them valued cognitive and motivational components of SRL. Primary and secondary school teachers need training to enhance their direct and indirect instruction of SRL. They could benefit in particular from learning about explicit instruction of SRL strategies and metacognition.