I'm going there tomorrow with some classmates and a teacher as a class trip, but it said the place was closed on weekdays. Does that mean we'll be the only ones there? I hope not...

November 5th and 6th are school days. The festival isn't open to the public on those days, it's just for students. https://www.texrenfest.com/school-days

Weekdays can be for school events, typically, so you'll probably be there with lots of other classes and maybe other schools?

We went on the weekend I don't think school year there open on weekends but just mapquest the renaissance Festival and it will show time's of the park