I have created a program that allows you to easily configure network proxy settings on your Raspberry Pi using a simple GUI. It is great for schools that filter websites using a proxy, and require the proxy to be configured to be able to access the internet. I spent a lot of time trying to get the internet to work on my Pi at school. After I figured it out, I had the idea to write a program that does it automatically at startup.
You can download it from https://pi-proxy.net/. The program costs nothing, but if you find it useful (and I hope you do), please donate a small amount.