That's a good question. Since the "warning label" made a specific distinction between "theory" and "fact" or an "established fact," we can assume that at least the school board does not consider a "theory" to be an "established fact." I was taught (in science classes) that one can test a theory through various means, such as lab experiments, and they would either confirm the theory, or show it to be inadequate. Most theories have gone through some form of revision as experiments have proven or disproven the validity of the theory. Darwin's theory defies confirmation through experimentation. One can show from experiements with fruit flies that genetic changes take place, and that some changes or adaptations are harmful or beneficial, and to some extent the concept of "natural selection" has been established, but no amount of fruit fly experiments in a lab has ever produced something that wasn't a fruit fly -- the rise of a new specie, as Darwinist theory maintains. At best, the Darwinist explanation (or the neo-Darwinist explanation) of the rise and diversity of species, specifically the rise of higher forms from lower or simplier forms, is just that -- an explanation, and a spectulative one at that -- and not a demonstrated fact. Hence, the school board's sticker seems quite appropriate. But the ACLU, certain parents who seem to have a slavish devotion to naturalistic materialism, and pretty much all scientists who derive their incomes and professional prestige from Darwin's theory, believe, and (here's the kicker) would require us all to believe under the authority of a federal court order that Darwin's speculative explanation is an established fact.
In scientific terms, a "theory" is a model or a description or explanation.
It doesn't presume to be a fact, and it's constantly open to revision based on new actual facts.
Using the layman's interpretation of "theory" to be the equivalent of "possible guess" is a semantic way of dissing the scientific process and what all scientific theories are.
Scientists would readily agree that a scientific theory is not a fact. Fact support theories, but they're two different concepts.
The sticker was a simplistic attempt to place scientific theory below actual fact, and that was dishonest. Facts lead to theories, not the other way around.
It really doesn't matter whether you can replicate evolution in a jar of fruit flies in two weeks. To argue against evolution using science as an argument is to be engaged full-time in rationalizing against the countless specimens in the fossil record, which generally involves believing all species on earth fit into an ark with one 18 inch window for ventilation.
It really comes down to a decision of whether you want to believe what you want to believe, or do you look at the facts and reach a conclusion based on them. I'd say that if you're spending your time trying to discount evidence, then you're headed toward believing what you want to believe.