Petaluma City Schools is preparing for a major board shake-up this November as three longtime trustees step down, leaving open seats across three trustee areas. The Petaluma Argus-Courier reports five local candidates have launched campaigns to help manage Sonoma County’s second-largest school district, which serves over seven thousand students across 17 campuses with a $137 million budget. In Trustee Area 2, special education advocate Brianne B…