Khan Academy is a non-profit education site that specializes in various topics, including math, physics and chemistry. It has a lot of quality content and is the perfect site for a Liceo student who wants to learn more or has a doubt in some topics. Khan Academy also offers test preparation (PSAT, SAT, GMAT).
Do you like code? This is the perfect website for you to learn. It teaches you various programing languages including: python, c++, html, css, java script, etc. Remember code is the future.