Web plugins are becoming a depreciated way to run content on the internet. Web browsers such as Microsoft Edge and Google Google Chrome is a web browser developed by Google and is available on most school PC's. If you are having trouble with certain websites, it is useful to try a different web browser to see if this fixes the problem. not longer support plugins such as Silverlight.
If you need to view content that includes a Silverlight object. Use Internet Explorer to open the web page, as this currently supports the older plugin model.