Which study would be categorized as research involving human subjects according to federal regulations?

The correct choice focuses on a study that involves assessment interactions with human subjects engaged in a particular task. In the case of "a study of reading comprehension assessments in classrooms," researchers are likely interacting with students directly as they perform reading tasks and answer questions designed to gauge their comprehension abilities. This interaction constitutes engagement with human subjects, which invokes the ethical and regulatory considerations outlined by federal regulations.

The other options involve activities that do not primarily engage human subjects in the same way. For instance, a survey of teachers about classroom conditions might involve professionals, but the core focus might be more on gathering opinions about their environments rather than direct interactions with student subjects. The observation of school events may gather data but does so passively rather than through structured intervention or interaction with the participants. Finally, a review of school funding allocations involves analyzing existing financial data, which does not include direct involvement with individuals as subjects, thus not meeting the criteria for research involving human subjects.