The paper gives Dutch results and possible implications of three recently completed international evaluation studies. School subjects were mathematics and science at the grade levels 8 and 9 in more than 500 schools. Effect and efficiency of teaching and textbooks in different school types, opportunity to learn, and students' classroom participation were studied. Results of a subsequent experiment involving training for teacher management and instructional behavior are reported. Data collection was by means of observations of eight lessons per teacher, tests and questionnaires for teachers and students. The training course was highly successful, with effect-sizes from .47 to 3.50. Recommendations for teacher training are given. (Author/JAZ)