They share a postcode, they share a border, and they're within about ten thousand dollars of each other. I get asked to pick between them constantly, so here's the honest comparison — including the bit where the two official sources flatly contradict each other.
The prices, and why they disagree
This is the part nobody explains properly. Two credible sources, two different answers about which suburb is dearer.
| Measure | St Agnes | Ridgehaven |
|---|---|---|
| Median, June quarter 2026 Valuer-General SA |
$905,000 17 sales, +11.7% |
$895,000 22 sales, +15.5% |
| Median, 12 months to June 2026 Cotality |
$852,000 51 sales, +5.4% |
$885,000 79 sales, +14.9% |
Read that carefully. On the most recent quarter, St Agnes is the dearer suburb by $10,000. On a rolling twelve months, Ridgehaven is dearer by $33,000. Both figures are correct.
What's actually going on: St Agnes had a strong quarter off a small number of sales (seventeen), which pulled its quarterly median up sharply while its twelve-month average stayed modest at +5.4%. Ridgehaven has been climbing steadily all year — +14.9% over twelve months across seventy-nine sales, which is a far bigger and more reliable sample.
My read: Ridgehaven has the more convincing growth story, because it's built on nearly five times as many sales. St Agnes's quarterly spike is real but it's the kind of number that can bounce back down next quarter. If you're weighing them purely on momentum, that's the honest distinction — and it's the opposite of what you'd conclude from a single headline figure.
Sources kept separate on purpose: the Valuer-General publishes a single quarter, Cotality a rolling twelve months. Blending them produces a comparison that looks precise and isn't. Same reasoning as in the Redwood Park price breakdown.
Schools: a real difference, and it matters here
This is where the two genuinely diverge, and it's the thing I'd actually base a decision on if you've got kids or plan to.
St Agnes
High school is split between Modbury High School and Banksia Park International High School. Part of the suburb also falls inside Ardtornish Primary's zone — one of only a handful of zoned primary schools in the area, which means a drawn boundary rather than a road-distance calculation.
Ridgehaven
High school is split between The Heights School and Banksia Park International. Ridgehaven Primary is unzoned, so primary placement comes down to which unzoned school is closest by road.
Both suburbs are split at high school level, so in neither case can you assume anything from the suburb name. Ridgehaven is the more evenly divided of the two — the boundary runs right through it.
If schooling is part of your decision, read the full school zones breakdown before you make an offer on anything. It has the thirty-second address check in it.
What you actually get for the money
Honestly? Very similar housing stock. Both are predominantly three and four bedroom homes on generous allotments, mostly built through the 1970s and 80s, and both are strongly owner-occupied rather than investor-held.
The differences are more about feel than value:
- Ridgehaven sits higher, so a decent number of homes get a view, and it's closer to the Tea Tree Plaza interchange and the O-Bahn.
- St Agnes is quieter and a bit more pocketed, with the Ardtornish zone giving part of it something Ridgehaven can't offer at all.
At a $10,000 to $33,000 gap on the median — depending which measure you believe — the price difference between them is inside the range of a single kitchen renovation. Don't pick a suburb over a difference that small. Pick the house.
So which one, if you're buying your first home?
The genuinely useful answer is that this is the wrong question, and I'd rather say so than pretend otherwise.
These two suburbs are close enough on price, stock and demographics that the variation between houses within either one is much larger than the variation between the suburbs. A tired house on a main road in Ridgehaven and a renovated one on a quiet street in Ridgehaven are further apart than Ridgehaven and St Agnes are.
Where I'd actually let it tip the decision:
Lean Ridgehaven if
You commute to the city and want the O-Bahn interchange close, you want the elevation, or you want the suburb with the more convincing recent growth record.
Lean St Agnes if
You want quiet over convenience, or the Ardtornish primary zone specifically matters to you — that one is a genuine, checkable difference rather than a matter of taste.
Otherwise: search both, and buy the better house. You will not regret it, and you'd be amazed how many people talk themselves out of the right home over a suburb boundary that doesn't mean much on the ground.
A note on timing
Both suburbs sit in a market with meaningfully more choice than a year ago — Adelaide listings around 41% above year-ago levels, properties taking longer to sell, and vendor discounting at a two-year high. As a first home buyer that's working in your favour for the first time in a while.
The one thing pulling the other way is borrowing capacity: the cash rate rose to 4.60% on 29 September 2026. If your pre-approval predates that, get it re-checked before you bid. Full detail in the current market update.
How I worked this out
Prices are from two independent sources, each shown with the period it covers: the Office of the Valuer-General's published quarterly sales data (free via data.sa.gov.au) and Cotality's rolling twelve-month figures. I've kept them in separate rows rather than picking whichever suited the argument.
School zoning is from the Department for Education's live zone service for the 2026 enrolment year. I've described which schools each suburb is split between without putting a percentage on the split, because the only number that matters is what the department's finder says about your specific address.
The comments about housing stock, elevation and feel are my own read from working both suburbs, and I've labelled them as that rather than dressing them up as data.
The bottom line
On the latest quarter St Agnes is dearer; over twelve months Ridgehaven is. Ridgehaven has the stronger growth record and it's built on a much larger sample, so I'd trust it more.
Both are split across two high school zones. Only St Agnes has a zoned primary school reaching into it.
And the gap between them is small enough that the house should decide it, not the suburb. If you want a hand working out which specific streets suit what you're after, that's exactly the conversation I like having.