Why, by demonstrating the historical, social and cultural life of Guarani and therefore, its indisputable value in the Reform Bilingual Education through the Teaching, being-in all cases, our workhorse the subject "grammatical differences between the Guarani and Castilian: contrastive analysis and its impact on education." 1.2. Statement of the Problem The results of the last national census, performed in Paraguay, in 1992, showed that 37% of the population of almost four and a half million inhabitants, is monolingual Guarani, 50% bilingual (Guarani-Castilian) , 7% monolingual Castilian and the remaining 6% speakers of other languages. However, until 1993, education was exclusively in Castilian, including: classes, textbooks and tests, by teachers with tremendous problems of oral communication and written in Castilian. Educational model that perversely helped to keep the majority of people outside of education, it actually reflected in the high rate of illiteracy, school dropouts and repeaters. The effect of still endure today as, according to statistics Ministry of Education and Culture, 67% of the economically active population of Paraguay is illiterate. What is one of the main reasons for this reality? The absence of the Guarani in Education. Paradoxically, today, thanks to bilingual education, that part of education in mother tongue, many native Guarani speaking children achieve democratic and critical learning, which, undoubtedly, the most valuable leads towards the goal of any human being supported freedom of knowledge. But the most important aspect of this fact, it already has and will have a direct and valuable impact, rather than individual development, in socio-economic, cultural and political development.