Typically with Angular you would be outputting these spans using the ngRepeat directive and (like in your case) each item would have an id. I know this is not true for all situations but it is typical if requesting data from a backend - objects in an array tend to have unique identifiers.
You can use this id to facilitate the toggling of classes on items in your list (see plunkr or code below).
Using the objects id's can also eliminate the undesirable effect when the $index (described in other answers) is messed up due to sorting in Angular.
Example Plunkr: http://plnkr.co/edit/na0gUec6cdMABK9L6drV
(basically apply the .active-selection class if the person.id is equal to $scope.activeClass - which we set when the user clicks an item.
Hope this helps someone, I've found expressions in ng-class to be very useful!
HTML
<ul>
<li ng-repeat="person in people"
data-ng-class="{'active-selection': person.id == activeClass}">
<a data-ng-click="selectPerson(person.id)">
{{person.name}}
</a>
</li>
</ul>
JS
app.controller('MainCtrl', function($scope) {
$scope.people = [{
id: "1",
name: "John",
}, {
id: "2",
name: "Lucy"
}, {
id: "3",
name: "Mark"
}, {
id: "4",
name: "Sam"
}];
$scope.selectPerson = function(id) {
$scope.activeClass = id;
console.log(id);
};
});
CSS:
.active-selection {
background-color: #eee;
}