Tennis balls (Charlton Kings GL53)

Hi,
I wondered if anyone has lots of old tennis balls that would be useful still for tennis please? Thinking 10+
I'm wondering if anyone works at a tennis club etc with access to some used but ok condition ones.

I work in a school and we are really low on tennis balls. We have re stocked before but they keep dwindling.

I can collect most evenings or weekends.
Kind regards