The role and functioning of schools are changing as well as what is expected of teachers (who face growing and diversified challenges); consequentially, well-being at the schools is endangered. As teachers and teachers' educators concern is: How to improve schools' and teachers' effectiveness and promote well-being. Believing that the path to effectiveness is through evidence-based practice, according to research results (meta-analysis and effect-sizes), the authors analyzed which factors have more impact on schools effectiveness; teachers arise as a significant factor, accounting for about 30% of the variance on pupils' achievement. So, the authors have searched for factors that have significant impact on teachers' effectiveness. Evidence shows that, among other factors, giving/receiving feedback, beliefs and expectations, self-efficacy, establishing clear goals, effective interpersonal communication, and classroom climate are determinant. In face of these findings, the authors have explored how NLP (neuro-linguistic programming) can contribute to improving teachers' effectiveness, through professional training. (Contains 2 tables, 8 figures, and 15 footnotes.)