"The theory is there are nine schools in the age groups, with years 5 and 6 dancing against all the other years 5 and 6 in the other schools, years 7 and 8 will do the same. There are two dances: the waltz and the cha-cha. There's a big group dance, a change of partner merengue that I'm going to get all the schools to do, so every couple there will do it." He says it's based on a Cuban rhythm. "After six counts of eight the kids change partners."
He says it's a good day for the kids with all the lights, glitz and glamour. It's taking place in the Whanganui War Memorial Centre.
"I bring the judges down: one from Auckland, two up from Wellington; Hamish [McDouall] is opening it for us. The kids get all dressed up and it's the whole nine yards.
"I'll do a running order of the day: we've got a Lady of Elegance, a Gentleman of Distinction — there will be a judge in the crowd judging that especially, watching the kids' deportment off the floor, activities on the floor, how they treat their partner, all that sort of thing."
Mark has ribbons, trophies and prizes ready for the occasion. There will be an overall school winner but couples will be recognised for their dance prowess.
Schools taking part are Ohakune, Churton, Kai-Iwi, Westmere, Fordell, Mosston, St George's, Upokongaro and St Mary's.
"Some schools only have years 5 and 6, while others have years 7 and 8 as well.
"The main comment I get from schools, apart from 'I didn't know Johnny could dance', is 'oh, they are getting on so well'. In fact, I went back into a hall to pick up something I left behind, and the teacher is having a debrief with the kids, and they were talking about the pros and cons [of dance lessons]. One of the pros was, 'the cha-cha was fun', and the con was, 'it was really hard when he turned the music on'. Because it was fast." The general feeling was one of enjoyment.
They call Mark "Mr G".
"I will promote the next stage up through my studio," he says. "That was always the plan ... if they want to take the next option.
"It was always the goal to take a couple from school through to the nationals podium and I finally managed that last year."
Winners in the Inter School Dancesport Challenge will get their dance in the spotlight, just like on TV.
Mark supplies the music with a carefully prepared playlist.
"It's about getting them out there and having a fun day."