When it comes to tossing caps in the air, Montgomery County Public Schools is once again No. 1.

The local school system has the highest graduation rate, at 87.6 percent, of the 50 largest school districts in the nation. It’s Montgomery’s fourth consecutive year in the top spot, while across-the-Potomac rival Fairfax County ranked second, with 85.5 percent of seniors graduating, according to the annual “Diplomas Count” report, published by Education Week.