Girls' Pure Cotton Striped School Dress

I bought this dress for my daughter who is starting Reception in September. She's almost 4 but bought size 5-6 as she's quite tall and figured she's more likely to wear is next summer anyway. So it was big but I expected that and think therefore think it's true to size. My daughter loved the dress when she tried it on so she wore it for the day, hence I have already washed it. Unfortunately it got very crumpled in the wash and although I have spent quite a while ironing it, I can't get some of the creases out which is a shame. Might do better if dried in the dryer rather than the line.