Concerns with educational quality have led to the implementation of external school evaluation (ESE), based on the premise that these processes can provide valuable information about schools and, consequently, create conditions for improvement. Improvement is based on the feedback, commonly in the form of an evaluation report, resulting from evaluations, describing the reality of each school, and providing clues and guidance for action and progress. Nonetheless, ESE still has a relatively weak impact on overall school improvement. With this in mind, this paper focuses on the potential of evaluation reports to promote improvement, aiming to answer the question: What kind of feedback on school self-evaluation (SSE) does ESE provide to schools? Focusing on the Portuguese case, the paper analyses the feedback regarding school self-evaluation provided in evaluation reports from the northern region of Portugal. The study concludes that the feedback provided in the reports is mainly descriptive and generic, referencing issues that apply to all schools rather than targeting issues specific to each school. This leads to the hypothesis that the vagueness of ESE feedback can explain the limited contribution external evaluations make towards SSE improvement in particular, and school improvement overall. The example of Portugal and self-evaluation can help bring to light where ESE processes are underperforming and require investment to achieve their goals.