Horizons - 4th Grade - Horizons (kindergarden throught sixth grade) uses a concept called spiral learning--a method that allows students to master concepts through the process of introduction, review, and reinforcement. In each lessons, a new concept is introduced, followed by some activities to practice that concept. In the rest of the lesson, students practice previously learned concepts, reinforcing what they've already learned. It's smooth, it's fast, and it's every effective.