I recently did this. I bought regular noodles in different shapes and put them in a ziploc bag. I put a little alcohol in the bag and food coloring and then shook it up.
Put rubbing alcohol (1-2 tablespoons), food coloring and rigatoni in a ziplock bag. Shake! Start with yellow and you can use the same bag a few times. Let it dry on newspaper.The aroma is strong so do it when the students have gone home. Avoid the rigatoni type noodles that are cut at an angle. They have sharp points.I have used various types of string over the years. We like to use regular string (not to thin). We dip one end in Elmer's glue so that about 2-3 inches of the string is wet with glue. Let the string dry over night. Then the end is stiff like a shoe string and the students can easily manipulate the string through the pasta. Attach a small tag (punch hole in it) to the other end of the string for the child's name. The tag will also serve to hold the rigatoni on while stringing. To really challenge them and keep them busy use smaller noodles. I like the rigatoni. You can use this same method for stringing fruitloops.
My kids do try to put them in their mouth, but never eat them. Most of them don't want to eat a raw noodle. I just simply remind them before we make them and then throughout the day that they can not eat them. I've heard of people substituting the alcohol for vinegar and it working just as well. It's totally up to you.