Practical laboratory work is intended to help students link theory with practice, learn about scientific methods, develop manipulative and observational skills and nurture professional attitudes.

Laboratory work has been one of the instructional means of teaching science. However, assessment of achievement in laboratory settings has often failed to reflect the more important objectives of learning in the laboratory.

We take as axiomatic that the fundamental reason for assessing students is to improve their learning, that we should develop forms of assessment, and that in science we should be encouraging students to learn a form of science as close to the way a practising scientist works as possible.

We agree with Woolnough, Toh and Hodson, that there are several dangers in certain types of assessment and to avoid them, it is necessary to make a holistic assessment based on whole investigations.

During the last four years we have try to improve our initial model with a repetitive process. With this model of laboratory work we have been able to give shape to a set of elements, rules and guide lines that allow to carry it out as similar as possible to a real investigation process.

The purpose of the present study is to describe an assessment model based on reporting and presenting the results. We have developed a form of reporting, which, we believe, enables a highly reliable assessment in a relatively simple way.