Recent work in forgetting and spacing of learning across long time scales suggests that which has been learned is easily forgotten. In order to be able to prevent this forgetting from happening in educational contexts, it is useful to understand how this forgetting occurs outside of the laboratory. Analyses are conducted of the time course of forgetting for declarative fact and Mathematics learning from computer assisted instruction systems, in order to see how forgetting occurs in ecologically valid contexts. The difference between the learning of declarative facts and Mathematics skills is compared and contrasted, showing that individual Mathematics questions behave similarly to fact learning, but that the learning of Mathematics skills may potentially have differing long term trajectories.