Wireless range problems

I am trying to connect 10 small apartments on a square parcel of land. I have 2 dsl connections and 2 wireless routers. I am only able to get good connectivity to about 4 apartments. I have tried an external router and wireless extenders. No luck. Is there a good piece of equipment, either an access point or a range extender that I haven't found yet that will solve my problem.

how big is "square"?

what are these buildings made of? tar paper shacks, 24" thick 30,000 PSI concrete, ???

regarding amplifiers, extenders, et cetera... WiFi is two way radio. more power on one end does not help the other end.

There are 5 duplexes in a square and each duplex is 1200 square feet. Walls are very thin and there is only a small courtyard, probably 50' x 50' that I refer to as the "quad". Exterior walls are stucco not concrete.

Thanks

I would start with a pair 12 dB omnis on a router in the quad, assuming that it is central.

no amps, range extenders or other snake oil.