The NY Times had an article ("The Trouble With Homework"). Some ways to improve the efficiency of your homework that they mention are:
- “Spaced repetition”: do every day a bit for each subject instead of trying to learn a subject at once. It provides the brain with the opportunity to build some strucure around the new knowledge.
- “retrieval practice”: test yourself and do tests at school. Tests force you to apply knowledge actively and as such they work better than passive consumption of knowledge.
- "cognitive disfluency": hardly readable texts, typing errors, weird fonts, etc. force you to more exertion. The effect is that the studied material is better remembered.
- "interleaving": mix different types of tasks.