Teachers who have strong content knowledge can be prone to thinking their student know more than they do. There’s actually a name for this, it’s called the “Expert blind spot.” This is especially common in mathematics and can result in students developing a shallow or procedural understanding of the content they’ve been taught because the teacher believes the students understand the mathematics behind the procedure. Formative assessment is as important for the teacher as it is for the students. Consistent formative assessment is critical.