This stacked bar chart shows the number of AP tests taken by the largest participating Massachusetts school districts each year, with each stack segment representing a unique district. The visualization uses the Vega-Lite API to encode the year on the x-axis, test count on the y-axis, and district as the color, with tooltips revealing school names. Data is loaded from a CSV file hosted in a GitHub gist, sourced from the MA DESE AP participation dataset, and rendered using the vega-lite and vega libraries with custom configuration for axis styling.