Mackillop took out the Don Moon Trophy after four days of play at the NSW Primary School Sports Association (PSSA) Championships in Inverell last week.
Mackillop won the boys overall and placed second in the girls. Sydney West were tournament runners up and they also won the girls overall championships.
CIS took silver in the boys championships. More than 100 boys and girls representing 13 associations enjoyed the hospitality of North West.
"We cannot thank North West School Sport enough together with Inverell council and Inverell Tennis Club for a fantastic week.
"Best of luck to our NSW team who will travel Perth in October for the School Sport Australia Championships," an organiser said.
Tennis convener Johnathan Russell and Matt Kerr from Heathcote Easte Public School were honoured with Tennis Service Awards at the presentation on Friday for their significant contributions to the sport for well over 10 years.