Canva.com is s a free graphic-design web based tool. Subscription is free, however, if you are asking your students to subscribe parental permission is required for students aged under 13 years. You can use it to design presentations and social media graphics as it has thousand of layouts. However, I currently use it to create tiles for my class SharePoint site.
Microsoft SharePoint is a browser based collaboration and document management platform from Microsoft. My school has Office 365 and SharePoint is part of the package. In simplest terms, it is the equivalent of have a class blog whether it be a Weebly site, Edublog or any other platform, with the advantage that it has a Windows interface (ie just like editing a word document) and the data can be hosted internally by a school or securely in the cloud. Great for school use, not so good for blogging.
Pixabay.com is my favourite Royalty Free website. All images and videos on Pixabay are released free of copyrights under Creative Commons CCO. You may download, modify, distribute, and use for anything you like, even for commercial applications. Attribution is not required. There are over 940,000 free photos to view and you can download images without having to subscribe. When teaching students about Creative Commons, I use this website.