The Rose Tree Media School District ranks 19 among 500 school districts in Pennsylvania, based on their performance on the Pennsylvania System of School Assessment (PSSA) Exam, according to the Pittsburgh Business Times.

The Pittsburgh Business Times recently released its 2012 Guide of Western Pennsylvania Schools. The guide lists the school district rankings on the PSSA scores statewide.

The formula for the ranking takes into account three years of PSSA test scores in math, reading, writing and science, according to The Business Journals. Three years of scores are considered, with the current year given the most weight.

Rose Tree Media School District ranked high in comparison to other Delaware County school districts. RTM ranked third out of 15 school districts in Delaware County.

This year, Rose Tree Media moved up their PSSA ranking from 21 out of 500 school districts in 2011 to 19 this year.

Here's how RTM ranked against other Delaware County school districts:

• Radnor School District – 4 out of 500
• Wallingford-Swarthmore School District – 13 out of 500
• Rose Tree Media School District - 19 out of 500
• Garnet Valley School District – 21 out of 500
• Springfield School District – 65 out of 500
• Haverford Township School District – 75 out of 500
• Marple Newtown School District - 83 out of 500
• Penn-Delco School District – 162 out of 500
• Interboro School District – 328 out of 500
• Ridley School District – 360 out of 500
• Upper Darby School District – 448 out of 500
• Chichester School District – 453 out of 500
• Southeast Delco School District – 479 out of 500
• William Penn School District – 488 out of 500
• Chester-Upland School District – 496 out of 500

In the Top 15 school districts category in Pennsylvania, Allegheny County was the number one county with six school districts represented, followed by Chester County with three school districts, Delaware County with two school districts and Montgomery County with two school districts.

For 2012 rankings, Upper St. Clair School District holds onto its first place title for the seventh year in a row, with Tredyffrin-Easttown Township School District dropping to third place and Unionville-Chadds Ford School District taking second place. Radnor Township School District stays in fourth place, Mt. Lebanon, North Allegheny and Hampton school districts came in at Nos. 5, 6 and 7, respectively. Lower Merion and Central Bucks school districts were next, with South Fayette rounding out the top 10.