How do I get stains (paint/pen etc) out of DD's school summer dresses? Help!

[juniperinNZ]

We're 2 weeks into our summer terms here and DD (5) has already managed to get various stains all over her two dresses. Some appear to be paint and/or felt tip, others are marks from either permanent marker (no idea why they give them these...) or whiteboard pens (she's not sure which...). I've put the dresses through a 40 degrees wash with stain removal on, then a 60 degrees with stain remover, but no luck... The dresses are a cotton/polyester mix, which we buy directly from the school and are pretty expensive so really don't want to buy more! Plus she is 5 so I expect her to continue to get messy .
Any ideas?

You don't, nothing removes white board pen not even white board cleaner.

It and, the scourge of any GCSE art student's mother, acrylic paint remain to haunt you as long as the uniform still fits.