In my spring Introduction to Art class we will be using two different types of acrylic mediums: regular molding paste and light molding paste. There are many types of acrylic mediums that artists use with acrylic paint to alter the characteristics of the paint and allow for a variety of different effects. The molding paste and light molding paste are non-toxic. However, I recommend that parents always supervise children while using the mediums. Liquitex and Golden both sell beginner sets that have a variety of different mediums in them for experimentation. They are a lot of fun.
However, for the purposes of the class you will only need the Regular Molding Paste and Light Molding Paste.
Golden is my favorite brand of acrylic mediums and they explain their mediums much better than I could here. Dick Blick Art Supplies also provides a lot of information about mediums on their website.
I generally buy my acrylic mediums at Michaels and I usually print a 40% off coupon such as this one that is good through this Saturday.
We will only be using these mediums for a couple projects so if they are out of the budget, don't worry, you will still be able to do lots of fun projects!