Butterfly nets. Big ones. On long poles. You know... for the kids. In the neighbourhood. Give them a bounty for each drone that they catch.
Or license hunter-killer drones in, around, and above prisons, with suitable background checks, traceability, etc. and then create a reality TV show, with real-world prizes! prizes! prizes!
Or, an auto-launched drone that, in responding to indications of an incoming drone, drags a small section of fine netting (of kevlar and/or fine wire) toward, and then over, the target drone.
At the very least, a program of very frequent but seemingly-random drone drops into the prison yards, involving packages of various sizes/masses holding various amounts of chalk dust, charcoal, dried-up paint chunks, gerbil poo, peanut shells, etc..