The E/R diagram wording is in the singular - e.g. 'A teacher teaches a class'.
So there would be a rectangle for 'teacher', a rectangle for 'class' and a diamond for 'teaches'.
However strictly speaking, yes, the modelling is of the sets, and is translated to tables such that 'teacher' is the table (set) of 'teachers' and 'class' is the table (set) of 'classes' and depending on the cardinality, the 'teaches' would probably be a 'teacher-class' table