Slider images (main banners) and your CTA (call-to-action) images on your home page need to be sized the SAME size before uploading.
It's a best practice to pre-size certain images on your site to a specified size before uploading them, otherwise, you will eventually end up with aesthetic issues. The images you upload to your website may be different dimensions. So, by pre-sizing them all to the same dimension first, you can trust that when you select the original (or any scaled version) of the image, they are all the same size. This is important to maintain the aesthetics of your web site.
For example, the featured slider images on your home page should all be sized to the same dimension to ensure a smooth transition from one image to the next. If the images are different sizes, then you may see white space under some images and different heights to images as they transition. SchoolStatus does, in fact, create 12 different sized images based on the size of your original, but none of them may be the exact size needed for the banner area of your home page. Your designer (or SchoolStatus support) can tell you the exact dimensions of your home page image sliders if you need help.
Conversely, if you're just dropping images into the content area of your site on a basic page, and you want to align it right and flow text around it, the auto-sized images are perfect. You only need to choose the size that is closest to that size when dropping in the image. GIF and PNG images should always be pre-cropped and you will want to select the Full (Optimized) size from the options given when selecting the image.
Here is a helpful tutorial about how to crop slider images before you upload them to your site.