The website http://www.kidzworld.com/article/4109-acting-workshops-to-hone-your-skills lists schools in three major parts of the country at which you might be able to find acting classes for your kids.
You can try a community or youth center to learn about acting classes for your children that will be appropriate for their ages. The KD Studio is a place where kids can takes acting classes.
Try going to www.childreninfilm.com.It is a site geared specifically towards informing parents and teachers with useful knowledge about children and the art of acting. There you will find many answers to your questions.
Since acting classes are best suited as local classes, your location is key. Wikipedia has a list of drama schools available here: http://en.wikipedia.org/wiki/Drama_school which covers the entire globe.
Some acting auditions or classes have a agent just staring you in the face and you don't know it. Try your best each time.
Open your local yellow pages and go to acting schools. You will also want to read some books on acting and lot's of acting books have lists of acting schools that your child can get some training.
There are many acting schools across the country. You can find them in the yellow pages or online. Here is a list http://www.acting-school-stop.com/acting-schools.html
modeling and acting
Some do and some don't.
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You don't have to have an degree for acting, just take some acting classes or courses to have some experience!
To take acting classes, search for a reputable school in your area. If you find one that interest you, ask for references or reviews from previous students to see if that school is worth attending.
If you are wanting to work in broadcasting some good classes would be speaking classes, journalism classes, writing classes and some acting would help as well.