Should mediation fail, either party can request the impasse be sent to fact finding. While fact finding sounds like a neutral investigation of a district's financial books to see if there is sufficient money to pay for an association's requested raise, it is not. It is mainly an adversarial hearing, much like arbitration.
Within ten days of requesting fact finding, a panel of three hearing officers is created: each side has five days to pick a panel member and PERB has five more days to choose the chairperson. The panel is allowed to request whatever records/documents it would like to look at, and at the hearing, the district and the union present evidence about comparable wages in other school districts, the district's ability to afford the requested wages, and such like.
While this is going on, the parties can still try to settle. If the dispute is not settled within 30 days after the appointment of the panel (longer if both sides agree) the panel makes findings of fact and recommends terms of settlement. They must be submitted in writing to the parties privately before they are made public, and the district has to make the findings and recommendations public within 10 days after their receipt. Note: the panels recommendations are advisory only; either side may reject them.