In my area (Tulsa, OK) a masters is preferred even for teaching clinicals as an adjunct (part time no more than 28 hours a week). I believe a masters in nursing (not an MBA or in another field) is required to become a full time instructor at the colleges, universities and tech schools here.
Where I teach, it's required to have a MSN to teach lecture or part- or full-time. It's required to have a MSN or be in-progress to teach clinicals or adjunct. My school is a LPN to ASN and ASN school.
In Southern California you can can have an ADN with many years experience and teach clinical for Lvns that is the minimum I have seen. I have also seen a LVN with a bachelors in something else teach clinicals and lecture this is at a community college.
Every state and potentially school is different. A master's degree was enough at one time but now many universities are requiring a PhD... check with your state board of nursing and look at the requirements of the job you are wanting..... like everything else in nursing, there are many roads to a single place, Good Luck!