One of the widely discussed issues in the current world is the quality of teacher’s professional competences, which is closely related to the possibilities and ways of their evaluation. The identification and evaluation of teacher's key professional competences is of particular interest for the team of researchers at Constantine the Philosopher University in Nitra (Slovakia) within the research project APVV-14-0446 Assessment of teacher's competences, the output of which should be a new concept of the assessment of teacher's professional competences and the design of a relevant set of assessment tools. The intention of the research team is to encourage teachers' evaluators to use more reflective approach to this task in order to ensure deeper feedback for teachers on their performance. The project started in 2015 and is still in progress. So far the team has managed to agree on 10 professional competences of teacher, which they consider to be the key ones for the high quality performance of teachers. Then, a new stratified approach to their assessment was developed, and for each of the competences, a set of assessment instruments: Assessment Sheets for evaluators, Self -Assessment Sheets for the evaluated teachers and instructions for Post-Observation Interview of the evaluator with the teacher, was designed. The instruments are currently being piloted in schools. The paper deals with partial results of the piloting of the three tools designed to assess the teacher's competence: can develop pupil's personality and their competences. The piloted tools will be introduced in more details and the issues connected with their acceptance and use by school staff and managers will be discussed.