This is just a short tip for you to tuck away the next time your preschooles are threading yarn.
Start by taping the end of your string or yarn to the table so it doesn't slide around. This will keep the items you are threading from sliding off the end!
Put a long, thin strip of tape on the other end of the string to form a "needle" for easier threading through the holes of your items. This will also keep yarn from fraying at the end as well.