It's odd how memory works, isn't it?

When the kids started school this week, I was trying to remember my classes and teachers from 8th grade.  I didn't expect to remember the teachers' names, but I expected to remember what courses I had; like, what I learned in math that year.  I could not.

I do remember 9th grade math, which was geometry.  I had class in the same room as my homeroom for 9th grade.  The name of the teacher is on the tip of my tongue.  I thought the guy was pretty cool until I had him for math, but he was just another math teacher, really.  But I don't remember 8th grade math at all.

10th-12th grade math classes I remember quite well.  I remember only an impression of 7th grade geography, where I'm waking up from a nap next to the persistently closed blinds in the dark classroom where Mr. Bates only ever showed slides.  I remember home economics, and ironing material to make tote bags, and being partnered with that popular girl who wore a new Swatch to class practically every week.  I remember the TRS-80's in the special education room, my 8th grade homeroom.  I remember my cousin, immigrated from another elementary school, sitting near me in my 7th grade homeroom, and her incredulity at my academic attention and proficiency, unsurprisingly not correlating the two.

During all of this reminiscing I had a flash of Indian Acres, a place where we used to spend summer weekends with my grandparents near the bay.  I remembered harvesting the peanut plants near the shed, playing rummy under the yellow porch light that didn't attract as many mosquitos, buying the complete set of Hardy Boys books at a flea market in the teepee-shaped community center, launching the boat at the dock, diving in the public dump for salvaged refrigerator magnets.  The details of these things exist in varied clarity in my mind.

But I can't remember 8th grade math class.

Clearly, I learned math that year, or I would not have progressed.  Still, it's somewhat distressing that I don't even remember the course.  Was it pre-algebra?  Was it algebra?  Did we do something else that year?  I simply don't recall.

What if life consisted only of what memories we have (doesn't it?), and we spent our lives struggling to hold on to what memories we meant to keep?  Am I missing something significant in 8th grade math?  What am I missing from my memory that can't similar be indexed by the mere fact that I know I experienced 8th grade math in the course of my education?