I've been using Excel for years, and COUNTIF is the way I do it too!
You would have thought that you could do it easily in the newer versions, but I've never really looked. I 'cut my teeth' on Excel 97, so I still use all the tricks I had to with that...
I've worked out how to do it using Pivot tables/chart BUT its a bit too complex along with COUNIFs for 11 yr old kids - a few will get the idea but it will over the head of most
The simplest way is to put the YES and NO's into separate columns.
Then you can use COUNTA on each column - it counts the non-blank cells.
TIP: the quickest way to separate YES/NO column into 2 is to copy the column and then do a Find & Replace on each column to remove the YES from one the NO from the other.