STEP 1.
Access the website ping.eu This website resolves the host and gives you the IP of the website. Hackers use the IP to DDoS the website, but we will not be DDoSing the website, we will be accessing it.

STEP 2.
Copy and paste the website IP into your web browser. This will usually bypass the school restrictions and allow you to browse almost any site.

STEP 3.
If step 1+2 didn't work, then come to this method. You will need a USB, and planning.

STEP 4.
Download Tor onto your USB while you're at home. Tor is a web browser created by programmers in Germany to allow the public to browse anything they want, completely anonymously. Your school will not be able to see what you're doing on your device, and Tor allows you to see any websites.