The pressure to achieve academically is a crime against learning
I do not think the pressure comes directly from the need for higher grades.  I think it come from how those grades are created.I my academic history (highschool, undergrad, law school, now teaching) I only felt real stress where grades were incremental.  Take my civpro class.  We had an assignment after only three lectures, an assignment worth 5% of our grade.  I had barely wrapped my head around law school and already my final grade, my scholarship, was on the line.  I did poorly on that assignment, immediately chopping a few points off my final grade.  On the other hand my crimlaw class had no assignments, just a big exam at the end.  That class allowed me the time to figure things out and was much less stressful.The highschool kids I talk to today are in a constant panic.  ((That's how I see it.  For them it's just normal.)) Grades are ridiculously high, with class averages well north of 90%.  So every test, every graded assignment, requires the focus of a final exam.  They cannot afford diversion or outside learning.  Each week is prep for the next test and each of those tests directly impacts their grade.  Have a bad week, or even a bad afternoon, and it might stick with you for years.  They don't dare read anything that isn't assigned for fear of not aligning with the teacher's "learning plan".  If it didn't come from teacher it isn't on next week's test and is therefore useless.  Imho this constant "exam mode" is the real source of stress.So drop the microtests.   Give them the one big exam and let them relax and learn at their own pace the rest of the time.