Basal readers are very structured. They are formatted in a way that gradually builds upon new knowledge. In fact, "basal" means basic. Beginning readers start by reading basic stories, constructed of short sentences, and applying simple skills. With each subsequent lesson, the passages and required skills become slightly more difficult to match the growing abilities of readers.
Vocabulary instruction is an important part of reading instruction. Students must learn to read unfamiliar words. In basal readers, vocabulary is introduced in a very controlled manner. Like the sentence structure of reading passages, vocabulary starts out simply and increases in difficulty as the reader improves. This easily decodable text is an identifying mark of basal readers.
Most teachers have the ability to create their own units, effectively planning activities for reading instruction. However, when creating units based on a short book or longer novel, for example, it is easy to miss an important skill because there is so much going on. Basal readers are designed to follow a planned, sequenced format as part of a spiral curriculum. This ensures that all required skills are taught and reviewed, circling back when necessary and applicable.
A basal reading series comes with a multitude of materials, including instructional supplements for the teacher and student workbooks. Workbooks are designed to correlate to the reading materials and skills that students are learning, thus offering opportunities for independent practice. Independent activities are either done in class or at home and always focus on reviewing what was learned rather than introducing new material.