By using Moodle interface I don't think so. You can do it by manipulating the Moodle database directly (handle with care!).
If you want to change this setting for all of the assignments, you could do execute the following SQL statement:
UPDATE mdl_assignment SET emailteachers=0 WHERE course IN (23,45,26)
23,45,26 are examples of courses id, you can change them with your own courses id.
This instruction will set emailteachers to "NO" for all of the assignments belonging to courses in the list.