Portuguese Language teaching has faced sustained challenges which address both theoretical and methodological issues towards its practice. Such issues refer to significant practices that provide pupils with a responsive language action. In this context, this paper aims to highlight misspellings which entail the interference of oral language into the writing of second year high school students. For this purpose, we seek to answer the following questions: what are the influences/marks of oral language in written texts of high school students? And how to handle these influences and reverse them according to the grammars of Standard Portuguese? Thus, in order to answer these questions, we support our discussion in light of the works of Marcuschi (2008; 2010); Fávero, et al. (2000); Kato (2002); Bortoni-Ricardo (2004; 2005). Through the analyses, we observed that although at the high school level, students still use oral language in their written texts, which implies either little knowledge of grammatical conventions or little mastery of the standard language. In addition, we believe that this influence may be a DOI: http://dx.doi.org/10.20873/uft.2359-3652.2017v4n2p167Revista Desafios –v. 04,n. 02, 2017168consequence of the lack of meaningful and oriented readings, which leads to a limited grammatical and enunciative repertoire.