[en] ABSTRACT: Reading comprehension is a complex and extensive process that the student can not face alone, therefore, the teacher must promote effective comprehension strategies because reading is the means to acquire knowledge. It depends on it, the success or failure of the school that conditions, in the long run, participation in society and personal fulfilment. The textbook is the pedagogical instrument present in most of the classrooms. Elementary School student's, without being yet competent readers, face their texts daily, whose contents are far from their knowledge. The composition of the teaching units their can favor or hinder the reading comprehension. The design favors the students their learning at reading competences provided that: the value of the texts is high, allowing the student to appreciate the reading as a source or knowledge; the organization of the didactic units has texts of introduction and review and that demonstrate planning; if the activities of the book cover central contents working all the levels of understanding and finally, if the format of the activities allows the student a high participation in the elaboration of the answers. The study is based on four didactic units from Natural Sciences in the fifth Elementary School course; two units of the Santillana publishing house and two units of the SM publishing house, to assess whether the design of their teaching units is conductive to reading comprehension. The results reflect that both publishing houses have dimensions that promote t reading comprehension and others that can be improved, although the most inclusive of all is SM. Reading comprehension is a complex and extensive process that the student can not face alone, therefore, the teacher must promote effective comprehension strategies because reading is the means to acquire knowledge. It depends on it, the success or failure of the school that conditions, in the long run, participation in society and personal fulfilment. The textbook is the pedagogical instrument present in most of the classrooms. Elementary School student's, without being yet competent readers, face their texts daily, whose contents are far from their knowledge. The composition of the teaching units their can favor or hinder the reading comprehension. The design favors the students their learning at reading competences provided that: the value of the texts is high, allowing the student to appreciate the reading as a source or knowledge; the organization of the didactic units has texts of introduction and review and that demonstrate planning; if the activities of the book cover central contents working all the levels of understanding and finally, if the format of the activities allows the student a high participation in the elaboration of the answers. The study is based on four didactic units from Natural Sciences in the fifth Elementary School course; two units of the Santillana publishing house and two units of the SM publishing house, to assess whether the design of their teaching units is conductive to reading comprehension. The results reflect that both publishing houses have dimensions that promote t reading comprehension and others that can be improved, although the most inclusive of all is SM.

[es] RESUMEN: La comprensión lectora es un proceso complejo y extenso al que no puede enfrentarse el alumno solo, por ello, el docente debe promover estrategias de comprensión eficaces ya que la lectura es el medio para adquirir conocimientos. De ella, depende el éxito o fracaso escolar condicionando, a la larga, la participación en la sociedad y la realización personal. El libro de texto es el instrumento pedagógico presente en la mayoría de las aulas. Los alumnos de Educación Primaria, sin ser aún lectores competentes, se enfrentan diariamente a sus textos, cuyos contenidos están alejados de sus conocimientos. La composición de las unidades didácticas puede favorecer u obstaculizar la comprensión lectora. El diseño de las unidades didácticas favorece al alumno el aprendizaje de las competencias lectoras, siempre que: el valor de los textos sea elevado, permitiendo al alumno apreciar la lectura como fuente de conocimiento; la organización de las unidades didácticas cuente con textos de introducción y repaso, favorecedores del procesamiento autorregulado de la lectura y demostrativos de un planificación previa; si las actividades del libro abordan contenidos centrales trabajando todos los niveles de comprensión y por último ,si el formato de las actividades permite al alumno una participación elevada en la elaboración de las respuestas. Se ha realizado el estudio de cuatro unidades didácticas de Ciencias de la Naturaleza de 5° curso de Educación Primaria; dos unidades de la editorial Santillana y dos unidades de la editorial SM, para valorar si su diseño es favorecedor de la comprensión lectora. Los resultados reflejan que las dos editoriales tienen dimensiones que promueven la comprensión lectora y otras mejorables aunque la editorial más completa es SM.