Through your years of schooling, you have been taught that the classroom does not exist in a nutshell. Outside factors influence a student's ability to work well in the classroom, and affect how they view certain issues. Study how philosophy, religion, politics and country of origin factor into the classroom. Other factors to consider are the students' socioeconomic status and if they need to work outside of school.
Consider the different types of education available today. Not all students thrive in a traditional public school. Consider standard private and religious schools, and how those types of education differ or are similar. Look at the programs available within a school itself. Compare and contrast how students in special-education courses, inclusion classes and advanced programs learn in the school. Consider distance learning and English as a Second Language learning as well.
If you decide to write about the different levels of education, you have options as to how you want to tackle such a topic. Focus on the primary, secondary or college level. Individuals planning to work within a particular level should focus on that level for the thesis. Look at how the students learn and what they bring into that level and what they take from it. Write about bridging from elementary to middle school, middle school to high school and so forth.
Perhaps you are not required to write a paper. In that case, consider engaging in some sort of proactive project. One idea would be an effort to promote literacy. You could also engage in tutoring or mentoring programs to help students. Student teachers might be able to reflect on their experience in the classroom; although this is a written assignment, a strong practical component exists in this situation.