www.compare-school-performance.service.gov.uk/find-a-school-in-england
That website has all the stats so a good place to have a look.
I think it’s worth thinking about secondary too as having to move areas during primary is a bit of unnecessary upheaval and stress.
Orpington is a good option. Other good options in the borough of Bromley would be Beckenham or Hayes (excellent primaries, non-selective secondaries and grammar schools).
Barnehurst gets a bit iffy for secondary as the non-selective options aren’t brilliant so I wouldn’t choose there.
Another area that might be of interest is my neck of the woods, Sutton. The station is in zone 5 and the trains go into Victoria, London Bridge and St Pancras (via City Thameslink). The town centre is large with a good range of shops, restaurants, a cinema etc. If you’d prefer a more ‘villagey’ feel, then Cheam Village, Carshalton Village or Carshalton Beeches are great options (all 1-1.5m from Sutton town centre if you need a pair of shoes/books/a musical instrument/art supplies etc so very convenient).
The area is very popular with families and there’s a lot to do with babies, toddlers and older children (lots of baby classes, a large play park as well as things such as ballet or tons of sports for the older ones eg cricket, bouldering, tennis, gymnastics and 100 other things).
Schools are fab offering a combination of excellent primaries, excellent non-selective secondaries and 5 grammar schools. For convenience, you could look near Manor Park Primary as it’s close to everything. If you want somewhere green and quieter, then Avenue Primary is a national teaching school with extensive grounds, own swimming pool etc. Lots of other great options too.