English spelling has always been described by many language researchers and teachers as a daunting task especially for learners whose first language is not English. This monograph presents the report of an investigation on the use of spelling, which includes the determining factor of grammar in the teaching of English, in it we will develop a program for observing students and teachers as an initial assessment, (pretest) and the design of the development of said observation as a final evaluation (posttest). This observation was made with the total of 28 students of the sixth grade of Primary School Nuestra Señora de Guadalupe, of which we only choose 6 which are the ones that are going through presented spelling difficulties according to the results obtained in the initial evaluation. Based on some activities proposed by the research team, activities related to the acquisition of the strategy to solve these difficulties in spelling were carried out. The students' types of spelling errors were detected, analyzed and then categorized according to Cook's (1999) classification of errors namely substitution, omission, insertion and transposition. The result of the observation was satisfactory since the objectives were met. And the results obtained at the end, compared to the initial results, show us a great advance in the development of the use of spelling as a determining factor in the teaching of English grammar.