This study aimed to identify the most required professional competences for schools' activities' specialists at the public schools in the Sultanate of „Oman , and reordering these competences according to the importance degree of their possession from the experts' prospective. After that, suggesting a set of practical suggestions for preparing and training schools' activities' specialists in the light of the professional competences necessary for them. The study followed the descriptive approach , where theoretical literature of competences were analyzed according to their concept types and deriving methods. Delphi technique was used through identifying opinions of 42 experts in the areas of educational administration, curriculum, and psychology inside and outside the Sultanate of Oman. The most important results for the field study in terms of the importance degree of each field from the expertsʼ prospective were as the following; in the personal competences field, there was approximate importance of 95-100%; in the planning competences field, there was approximate importance of 81-100%; in the professional development competences field, there was approximate importance of 79-100%; in the communication competences field, there was approximate importance of 83-100%; in the organization competences field , there was approximate importance of 83-100%; and in the assessment and follow up competences field , there was approximate importance of 88-100%. According to these results, a set of practical suggestions were proposed for the preparation and training of schools' activities' specialists in the light of the professional competences necessary for them.