WordPress (by default) will load a number of assets on the front-end of your Child Site, which will slow it down by adding a number of requests for features you may not be using.
Some of the requests that WordPress core adds on load include emojis, embeds, dashicons, jQuery migrate, XML-RPC, pingbacks, generator tag, short link, Windows live writer manifest tag, and the RSD generator.
There is an easy-to-use plugin called Better Speed, which will allow you to disable those assets from loading on the front-end of your site. After you have installed and activated the plugin it will add a sub-menu to settings in wp-admin;
Settings > Better Speed
Better Speed Settings
Select the WordPress core assets that you do not need to load, then click the save settings button. At the bottom of the setting page, it will show how many file requests have been reduced, as well as the site size that has been removed from the front-end of the site.
By removing WordPress core assets that do not need to be loaded on the front-end of the child site, it will end up reducing the number of requests on load, and reduce the size of the site for some minor gains.