You can read more about the WooCommerce grouped product type here - https://woocommerce.com/videos/woocommerce-grouped-product-overview/
Note: As training classes aren’t simple products, they need to be invisible on the archive shop page. Thus you should select the Hidden option for Catalog Visibility setting.
Note: Training products shouldn’t be visible on the archive shop page as well. Therefore, you should select the Hidden option for the Catalog Visibility setting.