National legislation concerning soil pollution by heavy metals in different countries is mostly based on the total heavy metal concentration levels allowed in different soils. As soil pollution is an issue of worldwide concern, here we develop a laboratory exercise for students in which they must check the suitability of a total metal concentration for soil pollution assessment. Undertaking two different Cu extractions promotes student discussion about soil pollution by heavy metals: Cu extracted with EDTA and Cu extracted with DTPA. These two extractions are commonly used by the soil science community to estimate the potentially available Cu for plants, which is compared with information about total Cu that is provided to the students. The results of this laboratory exercise demonstrate that the total concentration of Cu in the soil is not suitable for decision-making about whether a soil is polluted. However, establishing reference values from EDTA and DTPA extractions or EDTA/Total and DTPA/Total ratios may result in better indicators to establish the possible environmental risks from the presence of Cu in soils with which to make critical decisions about soil remediation strategies.