How can you use public school tennis courts?

Answer 1

Not exactly, but most public schools allow non-students to play (appropriately) on their tennis courts when not in use by the school or another organization authorized to access the facilities. They school is also within their legal rights to lock the gate and prohibit use of their courts.

Answer 2

Likely as not you'll need to contact the school. If the courts are locked you may need to register your name and potential pay for someone to unlock them. Technically, all Schiller property within a public school district is open to public access. Most districts have rules for accessing buildings and grounds, and if staff is reqired to be present youmay have to pay the wages necessary for that person to be present.