Like others on here have said over and over, there's a large difference between children and adults, and the ways that they need to be trained in certain areas.
Children need more of the psychological training than they do the physical training. That's not to say that they should stick to running an obstical course for an hour and not break a sweat. But I also don't think that kids, even if they're 10 years old to 14 years old, should be made to train in full contact situations. It's the same general rule for kids that age starting in weight lifting: their bodies are not devoloped enough yet to withstand the physical stress they would be putting on themselves.
If a kid...say, it's a boy, and he's 13...is sparring in class, I would fully expect him to have on no less than the headgear, chest protector, shin guards and mouthpiece. Now, he's a little more protected so that in case he does take a good shot, he's more able to withstand the punch or kick and can continue sparring. The goal for a kid that age when he's sparring shouldn't be to kick and puch his opponent full force, but rather to make enough contact against his opponent to let them know that they've been hit...but not a tapping hit, either...maybe about 60 - 75% force from a kid that age, as long as he's sparring someone around the same age and/or size.
The psychological training that I'm talking about is that kids need to understand that fighting is not a solution to a problem. The younger a kid is, the more raw their emotion is. Kids, from toddlers up to young adults (i.e. teenagers) don't have full control over their emotions yet. As a result, anger and fear can carry over into physical aggression...(I know it sounds like a "you don't know the power of the dark side" kind of thing, but hear me out). That's how kids work alot of things out...by fighting one another. It's a natural thing...not a good thing, but a natural thing. That's also why kids aren't fighting for their lives against one another...they're fighting because they're kids.
The one other aspect to that is that I think kids should be trained on how to handle a situation if they're put into danger by an adult...i.e. an adult trying to kidnap them or trying to harm them in any way. But this training doesn't have to involve busting a kid's nose to make sure they get the point. Teach them how to strike vital areas hard, how to scream for help, how to know when to start running, what to look for...things like that.
With adults, they need less psychological training and more physical training...most of the time, anyway. An adult's body is fully devoloped, and can withstand far more punishment than a child's body can. However, I still don't think that adults necessarily need to limp away from every class either. What good is training them if they can't come to the next class because they're always injured from going to class?
Now, don't misunderstand me. I'm a huge fan of how training was handled in the "old days". I started training at close to the end of the "old-school" training era, and was very fond of the training I received. I started when I was 12, and earned my 1st dan at 16.
I had my share of bumps, bruises, cuts, knots, sprains, over-extensions, bloodied lips, busted nose, busted knuckles, sore muscles...but the hard training wasn't just dumped on me in regards to rank. It should also be noted that I was big for my age, and always was growing up...so once I hit 13, I was put in the adult class and treated as an adult. There were other kids who started at the same time I did, that were a couple of years older than I was, but they were smaller than me. They weren't allowed to come to the adult class until they were around 16 or 17, when they had grown to a point that they could handle training as an adult.
Another example:
A friend of mine who was one of the adults that I used to train with opened a school some years ago in a neighboring town. He was qualified by our instructor to open the school, and seemed to be a fairly good instructor in his own right...as far as adults went. He would even admit that he wasn't sure how exactly to train the younger kids, because he was so used to hard training, that that was all he knew.
I remember that he got into it with a few parents when their kids went home with bloody noses after sparring class...it wasn't too long after that the parents starting pulling their kids out of the class, and he was forced to close the school.
He wasn't intentionally trying to hurt the kids, or have them hurt eachother. He just didn't understand how to train kids. Eventually, he ended up marrying a lady that he met through training that was also a blackbelt, and has since opened up a school in which she teaches the young kids, and he instructs the young adults to adults. Last I heard, they were doing pretty well. It just took some time go get the correct formula to be able to teach and be effective.
So, after reading the novella up there, the thing I hope the OP would get out of this is to recognize what kids need to train in general, and then work with training the kids with their individual needs. I'm not saying that the kids should be treated like China Dolls so they don't come home to Mommy and Daddy with their "fragile little feelings" hurt. But there is a pretty big difference between giving them McDojo training and banging them up.
It sounds like the OP, much like SteveBJJ suggested, would be more suited to teaching adults, and allow the kids to be instructed by someone who is used to teaching kids...and then learn from that person how to get the best results. It's ok to admit that you don't know how to train someone...and it's far better to admit it now than to train someone the wrong way over a period of time.
