This quantitative-qualitative research targets at understanding the insertion of foreign students in the Brazilian educational system and its effects, considering educational results and school interaction of these students and their families with school agents, the territory and borderland elements as the basis of the discussion. In the quantitative study, the nationality and borderland effects were described on the results of Prova Brasil regarding Brazilian schools and counties in its 2011, 2013 and 2015 editions. The analysis of multiple correlations and regressions evidenced the association between the relative rates of enrollments by foreign nationality students in the counties, the Brazilian school, their respective proficiencies and the negative effect that the geographical variable twin-cities attributed to the registered proficiencies. These findings directed the research s second study, in order to verify the effects of the foreign students insertion in a qualitative perspective of research, directly in the school. Observations and interviews were conducted with agents from two schools with high relative foreign nationality enrollment rates in the twin-city of Corumbá-MS. From the perspective established Brazilians and foreigner outsiders from Norbert Elias and John Scotson (2000), it became evident that the territorialities of frontier Brazilians and foreigners in the twin-city dictate negotiations about documental nationalities, ethnical identities and rights over the borderland space. This ends up entering the schools through the opinions of established Brazilians about foreign students and their outsider families.