The UNTEACH command is available to those "native" professional classes able to teach inherited semi-general skills like Herbs and Poisons, to those not otherwise naturally able to acquire these useful skills. Just as there are some egalitarian elders keen to spread the knowledge, there are others keen to prevent its spread for the sake of safe regulation.
Syntax: UNTEACH <skill> FROM <person>.
Catch the individual in your location and ensure he or she remains still for long enough to impose the UNTEACH reversal of non-native learning. UNTEACH requires you to be higher in the chosen skill than your target and for the person being untaught not to be one of the native professions i..e. he/she shouldn't have the skill as part of the innate guild skill-set. The UNTEACH is a direct action and once successful digs in the metaphorical 'claws' to strip out a lesson worth of learning. It takes a lesson from the one imposing UNTEACH to fuel this profound reversal of skill acquisition.
NOTE: should the unteaching retract the knowledge-worth of the very first lesson in the designated skill, the entire skill will be stripped from the memory of the non-native practitioner. This will set the person back to a state of complete beginner, requiring the 'first lesson' as per the stringent requirements detailed in HELP HERBALISM.