Schools, transport, amenities, lifestyle, affordability; there's so many variables.
It sounded to me like the OP meant the Western Suburbs along the Fremantle railway line. Generally the most expensive suburbs in Perth on the coast or the river, with a lot of the private schools and no doubt better state schools. I think the traffic is extra busy coming from that direction probably because they can afford to park or get a space at work, plus the inlet they're building cutting off Riverside Drive is going to stuff the CBD traffic further. From what I've heard though the Fremantle train is nowhere near as packed as the other lines.
If you meant the Northern Suburbs that can include anything North from adjacent to town, to all the way up the Northern corridor beyond the Northern Beaches. I live at the current end of the Joondalup line which is 30-35 minutes by train to the CBD plus short walks either end. Round my way Mindarie, Iluka, and Burns Beach would be more expensive lifestyle options within walking distance of the beach with a short drive to Clarkson or Currambine train stations. I've no idea about better schools though since I can't imagine we'd be able to afford more to move or pay privately, so my 4 yo daughter just goes to the local state primary.
For something a bit more European and city like, you could consider East Perth around Claissebrook, Subiaco, and Fremantle. Then you're walking distance to restaurants, shops, and in the first case, work.