We were based in Secret Harbour for our 3 week reccie. I really liked the place. It had a nice feeling and has a decent restaurant in the Whistling Kite. It's a short drive to Mandurah where we spent fair bit of time, although it's got a mixed reputation. It'll probably take you an hour to drive to the CBD, which isn't too bad if you can work from home a couple days a week. The car parks at the train stations are rammed at peak times.
The properties are really cheap to buy/rent compared with the northern suburbs. Not sure about schools but you can check out the rankings here https://www.watoday.com.au/national/western-australia/wa-school-atar-ranking-2019-how-did-your-school-perform-in-2019-20200108-p53psl.html .