I had a terrible time a couple years ago when my oldest daughter was in school and the teacher let the kids use dry erase markers during circle time. One boy seemed to always mark up my daughter’s clothing. (I know it was not my daughter because of the unreachable spots on her clothing where the stains occurred.) I tried many things to remove these stains. Finally, I tried something that seems to really work.
I use Murphy’s Oil Soap. I pour a little directly on the stain. I then rub it into a lather. The lather should start to take on the color of the marker as the stain comes away from the fabric. For a few stray spots, I use my fingernails to scrape back and forth while the soap is still there. Then, I rinse and launder as usual.
I just put a pair of my pants from teaching preschool in the wash after treating for a stray mark from one of my students. Now I can wear those pants again, instead of having to get a new pair for work.