Charlotte Mason found amazing success with the tool of short lessons. Lessons that spanned ten to fifteen minutes for elementary students. I have found this same tool to be extremely helpful in aiding my children's in retention. Here is why I believe this works:
Studies show that we remember only the very first part and the very last part of what we read or hear. Therefore, our children are not retaining much in the middle of the reading or listening session. However, with sort lessons, the beginning and end are much closer together. Thus, the amount of material in the middle is reduced.
The interesting thing is that those studies were done on adults. Why should we limit short lessons to little children with even shorter attention spans than adults? I believe older kids will also benefit from this technique. Perhaps we should break up a subject into two sessions. For example, read science for fifteen minutes. Do math for fifteen. Read literature for fifteen. Then repeat. The retention would be substantially increased. Or, we could have our older students implement five minute breaks in their longer subjects, breaking up the material for increased retention. Perhaps they could wash the dishes during the break!
Shorter lessons are so important for our children's ability to learn. Not only do children who are forced to sit at the table doing math for an hour begin to hate math and school, they also learn far less than the child who is given a short math lesson of ten to fifteen minutes.
I can say that after years of begging, pleading and falling into frustrated despair over my children's inattentiveness, I've stumbled upon the answer. Oh, how I wish I had believed in short lessons before I did so much damage.