ng-model isn't updating when selecting an option - angularjs

Question

I have a form with with option list
<form class="column-form">
<select id="classSelection" ng-change="classOptionChange()" ng-model="selectedClass" maxHeight="120">
<option selected value="">{{classOptions}}</option>
</select>
</form>
Sample class options is here
[{"id":"classR","text":" Color - Red"},{"id":"classG","text":"Color - Green"}, {"id":"classY","text":"Color - Yellow"}]
My directive is simple as I'm just trying to print out the value of my selected option. However, it's always null.
(function() {
appModule.directive('classDefault', [ '$translate', '$timeout', '$window', classService, function($translate, $timeout, $window, $document, classService) {
return {
restrict : 'E',
scope : {
.......
}
link : function(scope, element) {
scope.classOptionChange() = function() {
console.log(scope.selectedClass);
Any suggestions?
UPDATE - Thanks for all the suggestions below. Apparently, we are using this widget that supposed to render the option lists and then bind to the select tag but it is currently broken.

Answer 1

You need to bind the array to the select tag. One option to do so is to use the NgOptions directive.
Here's an working example
angular.module("app",[]).controller("ctrl", function($scope){
$scope.items = [{"id":"classR","text":" Color - Red"},{"id":"classG","text":"Color - Green"}, {"id":"classY","text":"Color - Yellow"}];
});
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.10/angular.min.js"></script>
<div ng-app="app" ng-controller="ctrl">
<select ng-change="classOptionChange()"
ng-model="selectedClass"
maxHeight="120"
ng-options="item as item.text for item in items">
</select>
<h3>{{selectedClass}}</h3>
</div>

Answer 2

It seems like you are not properly rendering all options that have been passed down to your directive. Ideally you should loop over the classOptions collection using ng-repeat/ng-options directive and render the select tag filled option's. And then specify ng-value-"opt" on each of your option element. That will basically help you assign whole option object to selectedClass ng-model.
Template
<form class="column-form">
<select id="classSelection"
ng-change="classOptionChange()" ng-model="selectedClass"
maxHeight="120">
<option selected value="">Select option</option>
<option ng-value="opt" ng-repeat="opt in classOptions">{{opt.text}}</option>
</select>
</form>
Demo Plunker