PCN has the finals, and I believe you can purchase a short-term subscription to access them on PCNTV
The NFHS (National Federation of High School Sports) is building an extensive network. By 2020, they claim that all games will be available via stream (no promises). I believe they have PIAA playoff games this year, but I'm not certain of that. Check for NFHS Network to see if they have the playoff games this year. (I don't remember any of the details, but NFHS Network also has a subscription charge to access.)