This question rests with the definition of evolution. The main problem in discussions about evolution and science arises when people use different meanings to the same word. People cannot understand each other if they are talking different languages and use different words for the same meaning. But people are aware of that and use dictionaries then. They are less aware, though, of the converse problem, so dictionaries are not applied or provide only rudimentary answers. Therefore everybody who enters the discussion has to define the terms he is going to talk about if it is not common sense, which it is less often than assumed.
There are people who define evolution as a fact. I’m rather inclined to support this. Facts are my hands, computer, and coffee mug. You can study these facts but you’ll never call them science. The difference between evolution and the facts mentioned above is that evolution is an abstract fact such as my ideas, but also economy, climate, population, insects and so on. These are also facts that can be studied by science but are not science itself.
Well some other people believe that evolution is science about evolution. This is not correct though. Throughout science we use different terms for facts and science about these facts to avoid namely this confusion. For instance climatology, → climate, entomologie → insects, psychology → my ideas and so on. Unfortunately we lack such a term to study the fact of evolution. This is probably because we have only one dominating theory about evolution, the Darwinian theory and its offspring. Once we have many theories, the fauceir theory for instance, we essentially need a term that describes the science that is focused on the fact of evolution, evolutionology or something like that.
Also some people equate evolution with the theory of evolution. This meaning of the term is not correct either as even before Darwin there existed several theories of evolution and sooner or later they will be numerous. Challenging this meaning of the term evolution as being not science is challenging the theory of evolution. Well of course every theory has to be checked whether it complies to the rules of science. But that a theory is consistent with these fundamental principles of science does not mean it cannot be improved. The history of science is a history of an steadily increasing number of theories. Some replacing some coexisting.
Finally there are people who understand evolution as a religion or at least as a backbone of a certain faith. This position can be found among supporters and critics likewise and of course if such a meaning of the term evolution is applied it is not science at all.