I'll explain, when I was a freshman and sophomore, they had a 50s day, a clash day, stuff like that. Did your HS do the same? Not sure if this was an 80s thing, or maybe it was just my school. The girls were more into the 50s thing than the guys, they would wear poodle skirts or the jeans rolled up.

Nope, not my school.  We did have days where we could wear regular clothes instead of our uniform.  The only time we were allowed to "dress-up" was for Halloween my senior year.

big deal.
is "wear a hat day" a theme?

No, the school went to didn't as far as I remember.

is "wear a hat day" a theme?

LOL! Sure, why not.

We used to have "theme days" in the week before Homecoming usually. I don't know if they still do it - it's been a long time.

Back in the early 90s, when the Blue Jays used to be good, my elementary school in Toronto used to have "Blue Jay day" where you were supposed to wear as much blue as possible. I don't know if they do it still, although I'm pretty sure they don't, since the Blue Jays hardly ever win anymore.

We also had "July in January day" when in January, the coldest month of winter, you were supposed to dress up in summer clothes and beach wear. We'd have a big assembly in the gym where they'd play "Kokomo" by the Beach Boys and other summer tunes. Of course, we had to change into those clothes after we got inside, since the weather was too cold to walk to school like that!

We used to have days like Twin Day, where you and a friend would dress a-like. 

During Spirit Week in October, each day would be a theme.  You could also by carnations to pass out to your fellow students that matched the color of the plaid in their skirt, since each grade had a different pattern.

Friday was always Senior Appreciation Day and the Pep Rally. 

We do Homecoming week, but since we wear uniforms there's not much we can do with it, and they're pretty much the same themes every year.

Because throughout the 80's I was in a private school, we had to wear uniforms. So, having a "Free Dress" day was like dress up for me. I remember a few times we got to go to the store for a special outfit just for that day. And, also my private school was a K-12 school, so a lot of the high schoolers would have their own dress up days, like Hippie Days, 50's style (the 50's were BIG in the 1980s), etc. Even later down the line (1990-1991), we had Biblical day where we got to dress up like shepherds and Moses and Ruth and all those people..

Oh yeah, we had dress-up days.  Like some of the previous posts stated, the 50s were hot in the early 80s.  We had a 50s dress-up day, and I think I was the ONLY boy who wore what the girls wore that day.. poodle skirt, saddle shoes, etc..  I always thought girls had the coolest clothes in the 50s, so I endured the teasing and had a blast fitting in with the 50s gals that day.

Apart from "skip school" day, nope.

I remember once we had a "past day" and a lot of us came dressed as greasers.  ;D

Well I don't know what high school kids in 1983 or 1984 were doing, as I was in elementary and middle school during the 80s, though technically I did start high school in the fall of 1989.   But I remember there were 50s days all the time.  There were also 60s days, a lot of 60s days in the late 80s.  I think around 1989 I noticed 70s days happening, most definately by the early 90s there more 70s days.

Both the 50s and 60s were very retro popular in the 80s.  So that's why it was a shock around the late 90s for many of us to find out there were.....gulp....1980s days!! 

Matter of fact, I remember some of the theme days from good ol' Sparks High (Class of '93).

There were: Get Back In Bed Day (we all showed up in our PJs), '50s Day, Winter Defiance Day (Those who were bold enough to dress for summer in the dead of winter did it; I impressed everyone by showing up in a tank top & a Speedo during a mild blizzard), Backwards Day, '80s Week (This was the ONLY one to ever get a whole week-Like, wow, gnarly, bitchin'-fer shurrrr!)

There was also Cowboy/Redneck/Hick Day, White Trash Day, and the ever-popular Roaring '20s Day (during which water guns were banned).

Yeah, we had dress up week. I can only remember Nerd Day though, because my cousin had a pee herman costume and I borrowed it for that day.