Sig. (2-tailed) shows us the probability of making a wrong conclusion. If the value is less than 0.05, we should conclude that there is a statistically significant difference. In our case Sig. (2-tailed) = 0, which means that there is a statistically significant difference between the achievements of the pupils and the way in which mathematics is taught. The null hypothesis is being rejected and the following alternative one is accepted i.e. Eta squared is calculated with the formula