Hi there, "What IS the meaning of...." Having a workshop means that you dedicate a few hours on a certain topic/craft/hobby where people get together just for that and learn from someone. Workshops usually only happen once or twice in a row but no more than that - it's not a class that's continous for a few weeks at a time. So in your example, during the students assembly, they are holding, or having a writing workshop, which proably means a workshop on how to write essays for instance... Hope this helps!

It could mean that once the students have assembled/gathered in the hall, they will listen to a lecture about writing essays/stories poems etc.