The FAA refers to the different types of airspace as Class A, B, C, D, E, and G. On the radio, B and D can be easily confused, so we use phonetics (Bravo or Delta), but when written it is not used that way.
This sounds reasonable. The term correctly written "Class B", so it is preferable to use the correct vernacular. Fixed.
Now when users enter the tag (c-l-a-s-s...), the text completion will show them the correct tag to use. Once the site gets moving along (past the private beta), the increased reputation requirements to create new tags will make it more difficult to enter the wrong thing. There's really no need to create a tag synonym because the text completion will automatically show them which tag they should be using.
And don't forget to add some helpful 'tag wiki' guidance to make tags even easier to use!