Your curriculum question is entirely dependent on the district/school. It can also vary by subject area. There are some schools (mine is one) that purchase very little packaged curricula, instead leaving it up to the teachers to plan and implement their instruction of the state standards according to how they see fit. There are other schools that rely exclusively on scripted curricula, where each lesson in each subject area for each day of the year is written out in full (I hope you are not teaching in one of those schools!). At my school for example, we recently purchased an excellent math curriculum, called Singapore Math, from which we draw most of our math lessons. We are always free to supplement or replace lessons with other resources or ideas (some administrations are okay with this flexibility and others are not – mine is). We also purchased a phonics intervention curriculum for struggling readers, and the lower grades use an English language development program as many of our students come in not speaking English. However, we have no packaged curriculum for reading or writing. Instead we draw from a wide range of resources and models to teach literacy. We likewise have no packaged curriculum for science or social studies, instead relying on units that teachers at the school have developed over the years and that improve steadily over time.
In my (unsolicited! :-)) opinion, as a new teacher it is incredibly helpful to be handed curriculum. The more the better. HOWEVER, it should come with the understanding that you are a professional educator who will decide when and how you want to use that curriculum and when you want to deviate from it according to your beliefs and the needs of your particular students. Too often these days teachers are denied the opportunity to use their creativity, innovation, and professional experience in deciding how to teach their own students.
Sorry for the rant. As you can see I have strong feelings about this issue. I’m sure your head teacher will be able to answer your questions more specifically about the district where you are student teaching.