Great community service project. High school students came in to the facility for seniors where I worked, to help do a Fourth of July project with the residents there. They helped them make these simple flags with wooden dowels (dowels can be purchased at Michael's or any other craft store) All you need is a printer, some wooden dowels and glue.
They are easy enough for children to do.

Below is a pdf file, which is a flag that you can print out on card stock paper. It's a mirror effect flag, after you cut it out, you put glue on the wrong side, put a wooden dowel in the middle and fold the flag with the dowel in the middle. Very simple.

I remember the seniors were so proud to put those flags around the entrance way of the facility on the Fourth of July, especially since they helped make them!