After explicit spelling instruction, low achieving second grade spellers increased the number of correctly spelled words during composing but differed in response trajectories. Class 1 (low initial and slow growth) had the lowest initial performance and improved at a relatively slow rate. Class 2 (high initial and fast growth) started higher than Class 1 but below Class 3 and improved at the fastest rate. Class 3 (highest initial but slow growth) had the highest initial performance but improved at a rate similar to Class 1. Class 3 differed from Classes 1 and 2 on orthographic coding. Classes 1, 2, and 3 differed on rapid automatic naming (RAN letters). Spelling instruction plus ...