This year the teacher next door and I are doing these with our Yr 1 (6 yr olds)classes and they are brilliant! Amy (other teacher) has made them at previous schools.
All you need is a wire coat hanger made into a circle (keep the hook) and about 1.5m of Christmas fabric cut into 16cm long x 5cm wide lengths. We have pooled all the kids different fabrics but you could do it with all the same. To make the wreath all you need to do is fold each piece of fabric in half length ways and tie onto the hanger. Its time consuming but as long as the kids can tie a knot they can do it themselves.Push the fabric close together as you go, then put ribbon over the hanger and tie a big bow. I will try and post some photos so you can see what it looks like cause I have to be honest I thought it sounded a bit dodgy when i heard it LOL