Creationism IS theology (see definition below). If it's taught in public schools it should be in a theology class and NOT in a science class. Personally, I would prefer that public schools use their limited resources to provide art and music classes and leave theology where is belongs in churches, synagogues, temples, et al. not in publicly funded schools.
Definition of theology (n) the·ol·o·gyc [ thee ólləjee ]
1. study of religion: the study of religion, especially the Christian faith and God's relation to the world
2. religious theory: a religious theory, school of thought, or system of belief
3. course of religious training: a course of specialized religious training, especially one intended to lead students to a vocation in the Christian Church (Bing Dictionary)
Bing Dictionary. Retrieved from http://www.bing.com/Dictionary/search?q=define+theology&qpvt=theology+definition&FORM=DTPDIA on September 24, 2012.
I’m leaving the U.S. Constitutional separation of church and state argument to others.