I wholly agree that head teachers should provide guidance when it comes to ethics, especially since many undergraduate programs to not have courses that center around ethical issues in education. However, it is important for head teachers to differentiate between ethical issues and issues of philosophy/methodology/personality. Head teacher should remember that each teacher is an individual, and that a different approach is not necessarily an unethical one.
This is an excellent question and one that is extremely important. I think the role of the head teacher is first of all to make other teachers aware that there are things that require ethics. It does no one any good to make believe that ethics does not exist in teaching. Second, lead teachers should discuss these matter candidly and even give possible scenarios that other teachers are likely to encounter. Third, the leader teachers should model principles of ethical principles in their daily lives. If the last point is not followed, I am sure that there will be little benefit in talking about ethics. Finally, periodic meetings where the staff are able to discuss issues will be important. In this way there will be support and counsel right from the beginning.
Many teachers who are new to the field may not have acquired enough wit (in a way, malice) to avoid or deflect conflicts that come as a result of the inevitable contact with other human beings. A head teacher can help new teachers by warning and modeling ways to avoid conflict: For example, how to avoid having parent conferences without a witness, to document everything that goes on with every student, to use developmentally appropriate language towards the students, to establish strong communication with parents, to understand frustrations from both co-workers as well as students and their parents, and to be a model of moderation and objectivity.
Younger teachers need much in the way of professional guidance. This takes on the form of understanding about the daily demands of teaching, pedagogical approaches, as well as practical tools which can help increase their effectiveness. Yet, the ethical dimension is one of the most powerful components of the professional or lead teacher. Teachers face ethical challenges on nearly every level as they teach. Lead teachers can serve as invaluable allies in this struggle. They can help to remind younger teachers of core values or vision, a paradigm which will allow them to fully understand how to make ethically viable decisions. Lead teachers can also model this through their daily practice to younger teachers so that they can see in real time how to navigate the ethical demands of teaching. Finally, the useful and meaningful presence of the lead or head teacher will prevent younger teachers from feeling alienated and alone, which might prompt them to make ethically challenged decisions.