On Saturday, the main western thoroughfare out of the CBD will become a sea of prospective students, as three universities and Sydney TAFE vie for business at their annual open days.

In the western corner, there is the nation's oldest higher education institution, the sandstone spires of the University of Sydney.

In the eastern corner, the brutalist concrete tower and fast-rising new facades of the University of Technology, Sydney.

And in the middle, a scrappy upstart with just 5000 students, the University of Notre Dame.

Strung along the road between the three institutions are the City of Sydney's advertising flagpoles, which have become the site of a secret proxy battle in the unis' ferocious war for students.

For 2015's open day, Notre Dame secured the flag bookings from Central to Abercrombie Street.

This, a source says, greatly displeased UTS, which did not enjoy having Notre Dame flags waving outside all its buildings for the coveted open day slot.

This year, UTS was able to secure the flags booking, earlier in the calendar than is usually possible. A source alleges intrigue.

Notre Dame and UTS did not wish to comment.

But a spokeswoman for the city confirms that while the flags are generally able to be booked up to six months in advance, the council agreed UTS could book the flags for this period "one month in advance of the booking lead-time to meet their financial year obligations". UTS did so in December 2015.

"When the city was later contacted by Notre Dame, the city offered a number of alternative banner locations within the same precinct," she adds.

"The banner bookings system is designed to be fair to all clients and maximise the banner locations and exposure."

Minus the flags to draw attention, Notre Dame - the David in this battle - will be instead touting its non-ATAR entry system and strong showing in the latest Good Universities Guide, where it scored highly on graduate employment rates and skills development.

UTS, which has about 40,000 students, is well into its $1.3 billion new campus redevelopment program with striking new buildings such as the planned UTS Central and the up and running Frank Gehry-designed Dr Chau Chak Wing Building. At open day it is offering a keynote talk on preparing for the jobs of tomorrow, tours of its 3D data arena and 15,000 free sausages at a BBQ on the Green.

The University of Sydney, typically able to rely on its prestigious reputation and campus lifestyle offerings for its 55,000 students, is touting open day tours of the Carillon spires and the new Nanoscience Hub, the chance to personally extract plant DNA, parent seminars about new mathematics prerequisites, and the Quidditch club.

Meanwhile Sydney TAFE says it has "everyday life covered", with courses from childcare to design, refrigeration and plumbing, and barista demonstrations. 

University open days in Sydney

The University of Sydney - Saturday August 27

University of Technology, Sydney - Saturday August 27

The University of Notre Dame - Saturday August 27

Western Sydney University - Sunday August 28

The University of New South Wales - Saturday September 3

Australian Catholic University (North Sydney) - Saturday September 3

Australian Catholic University (Strathfield) - Saturday September 10