I've been trying to remember this live action TV show for years now.
In it teenagers were able to enter this virtual world of sorts and they become these avatars. Their goal was to clear levels and move on to the next and I don't remember why. There were artifacts or items that help them on their way and they can return to the real world easily enough. I think they can re-enter the virtual world through someone's school.
To pinpoint a possible date I'm thinking maybe 2000s to 2004s, it is hard to remember because I was so young.