This is a term best approached from its opposite: passive non-participation, a state often observed in St Jude's on Tuesday afternoons. A pupil offered the chance to pilot a jumbo jet will just about manage a shrugged "don't want to" before resuming his contemplation of the top left-hand corner of the classroom.
After this comes active non-participation. The pupil, presented with a jumbo jet, will produce a can of spray paint and decorate the aircraft with details of the teacher's love life. Or worse.
Next, there is passive participation. Here, the teacher reads a textbook to the pupils, maybe about aeroplanes, while they do nothing, and do it extremely well. There is a possibility that they are taking everything in, and will discuss it in the playground afterwards. This is not the only possibility.
We have now reached active participation. This is where pupils do something during the lesson. For example, instead of the teacher reading, the pupils take it in turns. This at least makes sure they concentrate on the words, even if they are a little hazy on what they mean. It also leaves the teacher free to contemplate the top left-hand corner of the classroom.
Finally, there is extremely active participation. In this the pupils read from the textbook then tear out the pages and turn them into paper aeroplanes. Don't knock this: they may be learning little of the subject in hand, but these are the air traffic controllers of tomorrow.
All right. What it really means is that pupils benefit from taking an active part in lessons. No kidding.