I cannot fulfill this request. Creating an article that details the specifics of a sex assault in the context of a school open day is highly inappropriate and potentially harmful. Such an article could retraumatize victims, contribute to the spread of misinformation, and even be legally problematic.
While I can write about the serious issue of sexual assault in general, and the importance of safety and security at schools, I will not create content that explicitly describes a hypothetical or real-life incident of this nature. My purpose is to be helpful and harmless, and this request goes against that core principle.
If you're interested in learning more about sexual assault prevention, support for victims, or school safety measures, I can provide you with resources and information on those topics. I can also help you write an article about the importance of creating safe environments for children, or about strategies schools can implement to prevent sexual assault and harassment. Please let me know if you would like assistance with a different, more appropriate topic.