If your students are like mine, when their glue is clogged, they will try to jam anything into the tip to unclog it...a pencil, paperclip, etc. Sometimes, this works, but usually, it just stretches the tip out and eventually ruins it.
To prevent clogged glue, make sure students are always closing the glue bottles tightly!
1.) The first thing that I always do is close the clogged glue as tightly as I can and scrape off any dried glue with my fingernails. A lot of times, this will work.
2.) If the glue is still clogged, use a small pliers to take the tip off.
3.) Use a tissue to clean the glue off and a paperclip or other tool to pick off any dried glue. Replace the cap and you should be good to go!