Indeed, some of the most controversial elements being overturned or prohibited by the Every Student Succeeds Act were implemented not under No Child Left Behind but through the waiver system. It was through the waivers (and the Race to the Top grant program) that the Obama administration mandated test-score-based teacher evaluations.
Vinegar, bleach and borax powder are some examples. Bleach -- If you want to use something stronger than vinegar, then use bleach. Bleach is best used when the rings and stains are already too tough. Pour half a cup of powder into the toilet bowl. Leave it that way for a few hours before you flush the bleach away.
The black is from the mildew, mildew is from the wet mineral deposit and the mineral deposit is from hard water over the years. The solution is to clean your toilet bowl with a scale or lime removing cleaner. You can use acid, household vinegar, or a household cleaner to remove these deposits.