For the teaching in/on
 

In an email beginning to thank the teacher, are they correct?

-Thank you for your teaching in ___ (a course name like 19th Century Fiction or Special Topic in Danish Literature) in the previous term.
-Thank you for your teaching on ___ (a course name like 19th Century Fiction or Special Topic in Danish Literature) in the previous term.

of is the preposition

No preposition is needed.

Thank you for teaching 19th-century Fiction last term. (simple and straight-forward)
Thank you for your teaching English ... ('your teaching' is possible)

After 'your teaching', you can say 'of' if a course name is used.

To use 'in', you need to change 'teaching' to 'teachings', but 'instruction' or 'lessons' sounds better.
Thank you for your instruction/lessons in Danish Literature'.

To use 'on', 'lessons' can be used.
'About' may be substituted for 'on', with 'instruction' or 'lessons'.

Thank you.