The lowest you ask? Ohio Township at 15.8%.Outside of Allegheny county some anomalies: Valencia in Butler County comes in at 68.8%. I wondered if that was highest in the state, but it isn't even close. Millstone in Elk County clocks in at over 84% among others that are higher. Those young person voter drives really must go over well up there.
Ohio Township has one of the lowest numbers in the state other than maybe Green Hills Borough in Washington County at 11.8%.
Allthose factoids and more you can find by checking out the State Data Center's latest education dashboard.