I lived in what is becoming the environmental charter school for a few years, and my wife and I both did the following:
Cut through Frick Park to get to Reynolds Street in Point Breeze (there are several options, depending on where you live--through Shadyside Academy, one of the side streets close to Braddock, or Tuscarora).
Follow Reynolds to its end at Beechwood.
Take Fifth Avenue for one block (you can also cut over Mellow Park and take the sidewalk a few hundred feet).
Take Shady to Kentucky. Follow Kentucky to Aiken, then do a little jog along Aiken to Westminster. Follow that to Amberson, then take a right, then a left on Ellsworth. Follow Ellsworth to Neville, then take Neville to Fifth.
Not the most direct route, for sure, but generally very quiet.