School’s ultimate goal is to help all students to learn. This new approach to learning leads to a new culture of assessment (Dierick & Dochy, 2001). It is recognized that (i) assessment models centred on retention neither help learning, nor do they help to overcome school difficulties (Field; Kuczera & Pont, 2007); (ii) assessment can be a strong instrument for promoting learning (Wiliam, 2007); and (iii) formative assessment is acknowledged as basic in mathematics education and learning (NCTM, 2000). However, this new perspective of assessment hasn’t always been reflected in teachers’ practices (Black & Wiliam, 1998).

In the last five years, a Portugal-based Project AREA has developed an assessment for regulating the teaching and learning process. With a team of researchers and teachers from different teaching levels, this project aimed to develop, implement and evaluate assessment practices for mathematics learning in the 1st, 2nd and 3rd levels and high schools.

Our theoretical framework considered that learning isn’t a simple process of linear accumulation of parts. Instead, we view it as a transformation process, a change between levels of knowledge (theoretical or practical). This change happens by the action of the community inserted subject through the use of mediation tools (Engeström, 2009). It’s important that the student is able to understand the task before starting. This implies that the student should be aware of action development, trough the means at his/her disposal and the assessment criteria (Jorro, 2000). Therefore, intended interaction, which seeks to establish a connection between the learning aim that is implicit to the task to be performed and its performance output, is essential.

We use term “feedback” for the deliberate dialogue aiming to help students to overcome their difficulties by comparing the ″intended″ and the ″performed″ (Sadler, 1989). Feedback is the key element for formative assessment (Black & Wiliam, 1998). Nevertheless, one cannot say that the more feedback is given the better (Wiliam, 2007). It requires teacher’s pedagogical skills to be linked to several factors. In particular, a descriptive approach to feedback (Gipps, 1999), framing it as a dialogue (Jorro, 2000), focusing on the task or on the processing of the task or self-regulation (Hattie & Timperley, 2007) tend to be more effective. Feedback should never come up before the student has had the opportunity to think and work on a particular task (Black & Wiliam, 1998). But all assessment processes are inevitably social. Social and cultural differences, as well as epistemological, psychological and pedagogical concepts presented in the classroom may have a great influence in learning (Gipps, 1999).

The purpose of this study was to document students' factors that may affect the effectiveness of feedback in mathematics. In particular, we raised the following questions:

- How students with different mathematics academic backgrounds react to similar feedback?

- How students with different perceptions of mathematical tasks react to similar feedback?

- How students with different perceptions face to what is value by the teacher react to similar feedback?

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