Which tool should sixth grade students use to measure wind speed in their weather study?

The correct tool for measuring wind speed is an anemometer. An anemometer typically consists of rotating cups or blades that turn faster with stronger winds, providing a measurable indication of the wind's velocity. This makes it specifically designed for the purpose of wind measurement, which is essential in weather studies for understanding atmospheric conditions.

When conducting weather studies, students need to select instruments that accurately provide the data required for their experiments. Other tools listed serve different functions: a barometer measures atmospheric pressure, a thermometer measures temperature, and a rain gauge collects and quantifies precipitation, none of which are suited for measuring wind speed. Thus, an anemometer is the appropriate choice for this specific task.