Silat is about freedom of action, and children are the freest souls on the planet. A mental barrier such as: "I'm not sure I can do this" or "This looks difficult" tends to cripple the zest and energy of adults, but strangely, kids have no such qualms, which can be dangerous in many respects.
But, if we can learn to harness this curousity, energy and flexibility very early on, they will grow into much better pesilat than their older counterparts. The only difference between them, is experience.
A child has absoulely no past experience to speak of, thus, they have very little opportunity to have a Eureka moment the way most adults do. A wise man's words are often understood by the wise, and this takes years to develop within a pesilat. So, how do we go about passing on this knowledge to kids if we have nothing to draw upon? Maybe all we have to do is look to ourselves.
I remember being that kid studying silat when I was in school, and I remember the kinds of problems I gave my instructor (he's a guru utama of his own style now). I also remember why it was so boring to learn and what about studying silat made me so interested. It was the discovery, or lack of it.
As a child, discovery is important. I read somewhere that the foundation of happiness is discovery, of learning something that puts you in awe. The thing I most remember about studying silat as a child was discovering that my instructor could walk on thorns on the field and do backflips with ease. THAT was silat for me, not the jurus which pained me to repeat.
Children sometimes like to spar as a way to test themselves, prove that they have what it takes. More often, it's to emulate the 'martial arts' they see on television. One way of getting them to focus is to turn their learning into a contest, to see who can perform the jurus better, cleaner, prettier and pay attention to those who lag behind.
Get one of them to lead the class and rotate, so they understand what it feels like when their fellow students don't follow their orders. Sooner or later, they will all understand your frustration and toe the line.
Kids today are thinkers. They want to know WHY. Prove to them that by doing it the correct way, they can gain more leverage, or more balance, or more... etc and they will be more motivated to practice. Training children is a balancing act, for sure, but it's better to allow a child to learn the way they're used to, by playing.