How much time do you spend in school 1st through 12th grade Not counting at home or summer just IN school?

Let's estimate. A typical school year is about 180 days. Assuming a student attends school for 6 hours per day (this can vary by school and grade level), that's 1080 hours per school year.

Over 12 years of schooling (grades 1-12), that's 1080 hours/year * 12 years = 12,960 hours. This is a rough estimate; the actual number will vary depending on individual school schedules and any missed days.