So where and when do the standards suggest circle graphs be taught? They are certainly a part of daily life and students must understand what they represent.
I agree that bar graphs are wonderful and have a tight connection with the number line. Circle graphs are really nice to quickly view relative size compared to the whole. That is the reason they are used so often in newspapers and daily periodicals. They display information in a format easy for people to digest.
So, where should they be taught?
I value your insight and look forward to your guidance.