New Sidebar Template Not Working in Twenty Eleven

don’t edit twenty eleven directly; create a child theme and make the edits there.
it is important to have an unedited default theme in case of theme problems. also, any customisations of twenty eleven will be overwritten with the next upgrade of your wordpress version.

about the sidebar:
look into functions.php of Twenty Eleven, a few lines from the end:

if ( is_singular() && ! is_home() && ! is_page_template( 'showcase.php' ) && ! is_page_template( 'sidebar-page.php' ) )

that is the section where the sidebar appearance is controlled.

—
in the child theme of twenty eleven, add this to functions.php: https://pastebin.com/QVcpPus9

this should get your sidebar and page into the right position.

@ alchymyth…awesome, thanks!

I have added the following code to my child functions.php file,

add_filter(‘body_class’, ‘adjust_body_class’, 20, 2);
function adjust_body_class($wp_classes, $extra_classes) {

if( is_page_template(‘sidebar-preinsulated.php’) ) :
// Filter the body classes

foreach($wp_classes as $key => $value) {
if ($value == ‘singular’) unset($wp_classes[$key]);
}

endif;
// Add the extra classes back untouched
return array_merge($wp_classes, (array) $extra_classes );
}

I have more then one page template and this piece of code only works for one page template. Is there a way to modify this to add additional page templates ?

Thanks,
Mike

put all page template files using the || (OR) operator into the if statement:

if( is_page_template('sidebar-preinsulated.php') || is_page_template('another-page-template.php') || is_page_template('more-page-template.php') ) :

Thank you for your help, that worked like a charm !