Much of animation is similar to the rest of filmmaking: you need a narrative, composition, lighting, editing, a soundtrack etc. However, one of the main differences in animation is the timing, it's one of the fundamentals.
At its most simple: to create slower movements you need more frames of animation, for fast action you get away with less.
Students should be encouraged to understand speed, as you often find they go from one extreme to another. Upon realising their first animation appears too fast, they may start to create very slow sequences. It's a very tricky balance, especially when you are not too sure yourself, but it's heartbreaking when someone has painstakingly created beautiful but endless slow animation, for a rocket, or a sprinting hare!
Drawn animation provides a great way of understanding and learning about timing, as students can add new drawings (helpfully called 'inbetweens') in between existing drawings to slow action down, or remove drawings to speed action up.
British tv works at 25 frames per second (fps) so you could create 25 new frames for each second of screen time. This is called 'animating on ones'. However, it would be very laborious and no one does it.
Most commercial animation is filmed on twos, which looks nice and smooth, but fortunately animation still looks great if you film on threes (or even fours)
To record on threes what you do is (get the computer to) record 3 identical frames at a time, then when it is played back and run together, you have 8 still frames filling each second, and still looking pretty smooth (a fabulous two thirds saving in time and effort)
Of course, you can get away with fewer frames per second (animating on fours, sixes, etc) but after threes action can appear jerky and things that should be smooth (like a ball flying through the air) can look unacceptable.
Especially with drawn animation, students will often declare "That was quick! Can't we play it back a bit slower?". And indeed you can slow the playback down - say to half speed - however this doesn't really slow it down what it does is turns their animation into sixes, and their work usually becomes quite jumpy.
With older students you should get them to understand that 'jumpy' drawn animation can be fleshed out with 'inbetweens.' With other types of animation jerky movement can only be solved by working more slowly.
You will often find impatient students filming the same drawing twice or more - again to try and 'slow down' their work. This causes the same problems - however, there is a positive spin on this 'mistake' - they have subconciously grasped some of the fundamentals of animation timing.
For most younger students it is not essential they understand the difference between animating on twos or threes etc. What is important is that they understand how many pictures make up one second of screen time.
And if all the above is just gobbledgoop maybe try to imagine how jumpy your animation would look if you shot on 25s ie with just one new drawing per second
Most animation software can be set to film on threes, fours etc. If your software can't, it will probably be set to default and record on ones. If so, in order to film on threes, press the 'grab' or 'capture' button three times for each animated movement. Or better still switch to one of our recommended pieces of software.