PRINCIPALS have to be not only a good educationalist but also an excellent executive and public relations officer to cope with today's challenges, an academic said. Speaking on ''How Do Primary Principals Face the Challenges of the 90's?'' at a recent education conference, Mr Cheung Kwok-wah, lecturer of the Chinese University's Faculty of Education said principals had become more active in recent years. With the territory's political transformation and the provision of more education opportunities, schools had become more complicated, he said. ''Principals today have to negotiate with the Education Department and district board members and present their policies to parents. ''They can no longer work only in the school. They have to be active outside the school and they have to get involved in social and political affairs since the relationship between school administration and social development is getting closer,'' Mr Cheung said. He suggested principals work more independently of the Education Department and adjust to the dynamic education scene by co-ordinating with teachers. Mr Cheung's colleague, Dr Ng Ho-ming, spoke on ''School-based Staff Development''. He said teacher development played an important role in schools but external training courses conducted by the Education Department or tertiary institutes were inadequate. Dr Ng suggested school-based staff development. ''The main advantage of this method is its practicality. It deals with the concrete problems and needs of schools and students.'' He said school-based programmes would give teachers more opportunities to interact and would help establish rapport. ''They also give teachers a better understanding of the goals of the school.'' Dr Ng added that the implementation of professional development in schools should be carefully planned and divided into stages according to the situation of the school. He suggested the first stage be aimed at establishing a positive image of professional development in the school since teachers who always call for professional autonomy might be sceptical about the provision. The second stage is to establish an interactive framework through which professional development of the majority of teachers is taken care of. In the final stage, the objective is to establish an environment or a culture conducive to long-term professional development mainly initiated by teachers themselves.