You seem to have changed your plunker. The first one where you were using $http.jsonp call seems close but with CORs issues it is hard to test - you should definitely check the encoding type of your JSONP returned data is correct. However...
I would structure the $http.get as per the code below. Now that you have dropped $http.jsonp in favour of $http.get, also note that you may now need to explicitly unpack the returned JSON data string into a javascript object via jsonDecode. Lastly you will likely have to unwrap your server response to return just the json payload with no JSON_CALLBACK() wrapper.
var url = 'http://sitesbyjoe.com/angular-tests/typeahead/schools.php?callback=JSON_CALLBACK'
$http.get(url).success(function(data) {
console.log(data);
$scope.schools = angular.jsonDecode(data);
});