Update not working on laravel 5.1 using resource

Im getting Getting MethodNotAllowedHttpException in RouteCollection.php line 219:Store, create, edit are all working but when trying to update I get the error above.

{!! Form::model($enrollment['method'=>'POST','route'=>['/enrollment',$enrollment->id],'class'=>'form-horizontal']) !!}

                <div class="form-group">
                    <label for="subject_code" class="col-md-3 control-label">Subject Code</label>
                    <div class="col-md-8">
                        <select class="form-control" name="_method" value="PUT" id="subject_code">
                            <option value="{{ $enrollment->subject_code }}">{{ $enrollment->subject_code }}</option>
                            @foreach($subjects as $subject)
                                <option value="{{ $subject->subject_code }}">{{ $subject->subject_code}}</option>
                            @endforeach 
                        </select>
                    </div>

                </div>

                <div class="form-group">
                    <label for="subject_description" class="col-md-3 control-label">Subject description</label>
                    <div class="col-md-8">
                        <select class="form-control" name="subject_description" id="subject_description">
                            <option value="{{ $enrollment->subject_description }}">{{ $enrollment->subject_description }}</option>
                            @foreach($subjects as $subject)
                                <option value="{{ $subject->subject_description }}">{{ $subject->subject_description}}</option>
                            @endforeach 
                        </select>
                    </div>

                </div>


                <div class="form-group">
                    <label for="subject_code" class="col-md-3 control-label">Subject Code</label>
                    <div class="col-md-8">
                        <select class="form-control" name="subject_code" id="subject_code">
                            <option value="{{ $enrollment->section }}">{{ $enrollment->section}}</option>
                            @foreach($sections as $section)
                                <option value="{{ $section }}">{{ $section }}</option>
                            @endforeach
                        </select>
                    </div>

                </div>


                <div class="form-group">
                    <label for="subject_code" class="col-md-3 control-label">Subject Code</label>
                    <div class="col-md-8">
                        <select class="form-control" name="subject_code" id="subject_code">
                            <option value="{{ $enrollment->schedule }}">{{ $enrollment->schedule }}</option>
                            @foreach($subjects as $subject)
                                <option value="{{ $subject->schedule }}">{{ $subject->schedule}}</option>
                            @endforeach 
                        </select>
                    </div>

                </div>  

                <div class="form-group">
                    <label for="subject_code" class="col-md-3 control-label">Subject Code</label>
                    <div class="col-md-8">
                        <select class="form-control" name="subject_code" id="subject_code">
                            <option value="{{ $enrollment->no_of_units }}">{{ $enrollment->no_of_units }}</option>
                            @foreach($subjects as $subject)
                                <option value="{{ $subject->no_of_units }}">{{ $subject->no_of_units}}</option>
                            @endforeach 
                        </select>
                    </div>

                </div>
                <div class="form-group">
                    <div class="col-md-7 col-md-offset-3">

                        <button type="submit" class="btn btn-success">
                            <i class="fa fa-save"></i>
                            &nbsp;Save Changes
                        </button>

                        <button type="submit" class="btn btn-danger">
                            <i class="fa fa-times-circle"></i>
                            &nbsp;Delete
                        </button>
                    </div>
                </div>                                                                              
{!! Form::close() !!}

Here's my EnrollmentController:

    public function update(EnrollmentRequest $request, $id)
{
    $enrollment = Enrollment::findOrFail($id);
    $enrollment->update($request->all());
    return redirect('/enrollment');
}

routes.php

// Authentication routes...
Route::get('auth/login', 'Auth\AuthController@getLogin');
Route::post('auth/login', 'Auth\AuthController@postLogin');
Route::get('auth/logout', 'Auth\AuthController@getLogout');

// Registration routes...
Route::get('auth/register', 'Auth\AuthController@getRegister');
Route::post('auth/register', 'Auth\AuthController@postRegister');

Route::resource('enrollment','EnrollmentController');

via Chebli Mohamed