A Gym victory would break a three-game losing streak against their arch rivals. The fixture kicks off at 4pm and will be live on SuperSport.
Gym, who have only been beaten once this season, are ranked fourth on the unofficial national rankings, while Boys, who have lost four times, are a lowly 17.
With that in mind, neither camp enjoys the tag of favourites because it brings with it added pressure from the 20000-strong crowd split evenly in terms of support.
That said, Boys High, who are celebrating their 150th anniversary, are the clear underdogs.
The class of 2018 have it all to do and know their rivals’ supporters will be baying for blood.
Boys’ three-year reign began during 2014, and produced over 50 consecutive victories in South Africa and only one defeat - to Christchurch Boys’ High.
Boys High started 2018 as the top-ranked team in the country, but were seen off 19-10 by the Jaquares of Argentina at the inaugural World Schools Festival in Paarl.
Then came defeats to Grey College (20-34) and Paul Roos (8-44) as well as a shock loss to Oakdale (29-47).
Boys High returned to winning ways last week in a hard-fought 25-10 win at Sacs.
Their pack laid the foundation and once again their forwards will have to do the hard craft to make a fist of it.
Key players are their three SA Schools representatives, Adrian Alberts (captain and lock), Evan Roos (eighthman) and Roubert Bester (prop).
Lanky Alberts and the strongly-built Roos are at their most dangerous in the score zone and both are not afraid to put their bodies on the line in the physical skirmishes.
Whether the back seven can find the key to unlock a well-organised Gym defence remains to be seen.
The halfback pairing of scrumhalf Simon Carstens and flyhalf Estiaan van Rensburg will need to be at the peak of their powers and their decision-making could play a big role in the outcome.
Gym have once again had a great season with the boys in green, maroon and gold suffering just one defeat from 16 outings, to Paul Roos (13-32).
But now comes the acid test for a side that ultimately decides their season.
They have four WP Craven Week and one SA Schools player in their ranks.
They are former SA School cap Dawid Kellerman (centre), Stravino Jacobs (left wing - SA Schools), Bobby Alexander (scrumhalf) and Juan Beukes (lock),
Kellerman was a surprise omission from the SA Schools squad after scoring several tries during Craven Week, so could be out to prove the national selectors wrong.
Jacobs has plenty of pace and given half a chance will inflict damage, especially in broken play.
And watch Alexander, he’s a handful around the scrum and ruck fringes.
“This is an encounter that decides a season,” said Gym’s coach, former Springbok Pieter Rossouw, who took over in 2016.
“Such a pressure affair and neither team wants to end up on the wrong side of the result.
“But both sets of players will lap up the occasion and for sure will leave everything out on the field.
“Let me say that our opponents will come at us hard, as is always the case.”
His outgoing counterpart, Sean Erasmus, who is the new SA Schools coach, is looking forward to the clash.
“It’s a huge fixture and one we’re proud to be a part of.
“All respect to Gym, they play the game the way it’s meant to be played.
“I’m not going to make predictions other than to say my boys are raring to go and want their winning run to stay intact.”