The purpose of this researching study was to develop a teaching proposal and investigate the conceptualizations that children make about the processes of plants (photosynthesis, respiration, transpiration). We undertook an innovative implementation on teaching living things to students of 10 to 11 years old (5th grade). The theoretical framework is the Cultural-Historical Activity Theory that is inherently developed to understand the use of tools in human activity. The researching methodology followed a qualitative design, involving classroom observations and data analysis. The data were classified as students' arguments before the implementation and students' arguments after the implementation. Also, we analyzed how biology education is progressing at schools, under the Cultural-Historical Activity Theory framework. The findings and the results of the analysis were very optimistic and promising. Students participated actively in all educational actions and achieved the goals of teaching the plant processes. Students were able after the teaching to explain in simple terms the concepts of plant processes and also developed positive attitudes and values about living things.