I've probably taken more than 200 university credits so far, many including design principles and education philosophies. I've also been on the other end as a teacher for 6 years. This is a summation of the core principles that I found are essential to creating the most effective teaching materials.
Keep it short & simple.
I firmly believe the idea of "if you can't explain it simply, you don't understand it". When I teach, that's exactly how I feel. My ability to teach something quicker is a measurement of how well I understand it. This is rooted in well accepted educational theories as well. People learn in short bursts. They're more likely to retain knowledge presented in short 5 minute chunks, which can then be repeated for retention. Teaching it short and simply allows all people to learn (like learning disabled people) and makes it easier for everyone else to learn better and faster; so it's a win-win.
Additionally, it easier to keep people motivated. Looking at the peak of the mountain is intimidating, but making smaller goals on your way to the top makes it easier to tackle big challenges.
Favor concrete over abstract
Check out this explanation:
In probability theory and statistics, the binomial distribution with parameters n and p is the discrete probability distribution of the number of successes in a sequence of n independent experiments, each asking a yes–no question, and each with its own boolean-valued outcome: a random variable containing single bit of information: success/yes/true/one (with probability p) or failure/no/false/zero (with probability q = 1 − p). - Wikipedia
Now read this explanation:
Binomial distribution answers this question: If there are 2 possible outcomes, A or B, what is the probability that A will occur X amount of times over Y trials? Use the equation below, where P is the probability that A occurs in a single trial & Q is the probability that B occurs in a single trial.
For example, the probability of a rolling 1 through 5 on a 6 sided die 8 times out of 10 rolls would be:
Which one does a better job of teaching Binomial Distribution? Obviously the second one. It follows a formula. Start with "what is the point?". Then explain how to solve it. Finish with a simple example. Once you've gotten the point across, you can start augmenting a person's understanding of the concept. In this example, that might include the observation that P = P^-1, the short hand notation, or extracting meaningful information about the variance and standard deviation of binomial distributions. But it should always start with a simple, concrete example!
One at a time.
Your brain can do multiple associative tasks but only one cognitive task at a time.
An associative task uses conditioned memory, which is when you've done the task so many times, you don't have to actively think about it to do it. Hence the phrase, "you never forget how to ride a bike". It's using preprocessed data in your brain. That's why you can drive a car (associative task) and talk (cognitive task) at the same time.
Cognitive tasks do not use preprocessed memory and are instead creating new ones. They require active processing and learning, and therefore, you can only do one at a time. So if you're driving your car and talking, and suddenly it starts raining and you have to dodge debris on the road, you're going to stop talking, because now this unexpected kind of driving is a cognitive task.
Learning is always a cognitive task! I don't like seeing textbooks with pictures on the right, graphs on the left, colored boxes in the corner, and paragraphs all over the place. We all learn one thing at a time, so it should be presented that way.
Passive learning 20%. Active Learning 80%.
Passive learning is like a lecture. You just receive the information. Active learning is putting that information into practice. Schools already follow this principle to a certain extent. You've probably heard that for every hour of school credit, you spend two hours studying. So for a 15 hour credit schedule, you'll spend another 30 hours doing homework and studying. That's a 33% to 66% ratio. The 20% to 80% ratio works best.
This is one reason why I don't like MOOCS and think that new EdTech sites that rely heavily on long videos (longer than 3 to 4 minutes) have such poor results. Without the active learning, which reinforces to the student that they're making progress, the results are usually low completion rates and poor knowledge retention.
This quote kind of sums it up: "I hear and I forget. I see and I remember. I do and I understand."
The more ways you see it, the more you get it.
There is an unfortunate pervasive belief that people have learning styles. In reality, no such thing exists. They're mainly used as a defense mechanism. When someone does poorly at a subject, they just assume they're not a "math person" or whatever subject they're struggling with.
But the truth is that we can learn in any style and the more ways we see an idea expressed, the better we understand it. People tend to get frustrated when one resource fails them and they have no other alternative to go to. It's the seed to the learning style concept. Defeating that belief requires the ability to access learning materials of all different kinds of formats and perpectives.
One tool to rule them all.
I've seen some pretty amazing resources made, but they're all created using different technology like HTML, LaTeX, Word, Docs, Power Point, Video, PDF, etc. That makes it too difficult to share resources. There should exist one software that can create and open all of the different formats a teacher needs in a single easy to read window. Then, creating and sharing becomes easy.