The Dream Act gives in-state status to students who have attended and graduated from high school in that state . . . even if the student is not a legal resident of the US. A student who qualifies under the Dream Act would thus be eligible for both lower (in-state) tuition. In a few cases, Dream Act students would also be eligible for any financial aid that is provided by the state to its lower income students.
The Dream Act is only a state
program, though - not a federal program. Even though federal legislation has been pending for years, it is still not yet law. So the Dream Act would help you only if you are attending high school in one of the 13 states that have passed their own versions of the Dream Act. (See this article
about the Dream Act.) And, of those 13 states, only three (California, Texas & New Mexico) provide financial aid for their Dream Act students. So, if you live in a Dream Act state that's not one of those three, you are still going to have to pay the full cost of in-state tuition yourself.
But you might have other options. If you are not a U.S. citizen (or legal resident), then you wouldn't be eligible for federal aid . . . but that doesn't mean that private colleges might not elect to fund you directly, with their own need-based financial aid funds. Someone else on this forum might be better able to advise you regarding the options available to an illegal immigrant.
The one thing you need to know, though, is that the private colleges and universities that provide the best need-based financial aid are also the most difficult schools to gain admission to . . . so you really need to do well in school this year. And you also need to prep as much as you can for any standardized tests you'll be doing this year - such as the PSAT (in the fall) and ACT or SAT (in the spring or early summer).