On the basis of research and the syllabi for mathematics and environmental education, which promote integrated teaching, a model of integrated teaching of mathematics and environmental education has been designed. 331 basic school second grade pupils participated in the experiment (163 pupils in the experimental group and 168 in the control group). The differences in the results were statistically significant after the second test, as compared to the control group, the experimental group performed better at all levels of TIMSS taxonomy. With this the importance of interdisciplinary integration or of holistic teaching, indispensable in the first years of schooling, was confirmed.