Style.css in child theme is loaded before Bootstrap

Mostly the parent theme might be enqueing the child theme’s style.css, if so you can dequeue it by using handle and then enqueue with proper dependency.

If the child theme’s handle is child-theme-style, then dequeue it using

wp_dequeue_style('child-theme-style')

then enqueue it as needed like so.

wp_enqueue_style('child-theme-dep',get_stylesheet_uri(),array('bootstrap-handle-here'))

enter image description here

We can easily know the child theme stylesheet url by looking at the link output in the head, for example in the attached image.

<link rel="stylesheet" id='hybrid-style-css'  href="https://wptavern.com/wp-content/themes/stargazer-child-dev/style.css?ver=4.6.1" type="text/css" media="all" />

Tells us that the child theme’s enqueue handle is hybrid-style which is the id without -css.