A recent study in one school in Britain has shown that Facebook has very negative impact on the performance of students in school. What is all about? The school has conducted research and testing to determine whether social networks, and facebook as the most popular among them, affecting in any way the performance of students. The testing was done so that for a period of three months, the first two months access to facebook was denied and the third month access to facebook was allowed. The results showed that a sample of three months was just enough to make a conclusion. In the third month, during the period of facebook usage, it was noticed slight deterioration of grades, but what is even more important is lack of concentration and poor knowledge acceptance. In order to test the concentration level and the quality of teaching, at the last week, lesson was carried out to make summary of what was learned in every subject. In that summary students have participated and it turned out that the results were much worse in the third month. This test has shown that facebook and other social networks have the most negative influence on quality of education. The problem does not occur only in case when students were actually logged on to facebook and didn’t pay attention to what teacher says. The problem is in the fact that "current events" on the facebook distract them also in the time when they are not connected to it. Social networks are used by teenagers as a way to call the meeting with some person, to declare love and so on which in aspect of socialization is much easier to do than in actual world! In those situations, waiting for a response creates the need for constantly visiting facebook. All this mentioned, and many other elements are the reason why the results of the test showed that the use of social networks in school has a negative impact on grades, monitoring of teaching and the concentration of students. One more reason to block facebook in schools.