The most vivid part of the movie I can remember is the intro. It started out with a girl walking in this house. She walks to the end of the hallway and opens the door. Inside the room is a giant spider. I think this was a dream that she had. Then, she moves with her family to a new house and a new school. She meets new friends. The popular girl is a witch. I vaguely remember the rest. There was a portal through the popular girl’s locker that led them to this field. There’s a castle that the popular girl lives in, I guess? But the popular girl (the witch) turns into a dragon and the main characters have to defeat her to help their friend.
I cannot remember the decade this movie was made but it has to be no later than 2007. I believe it might be late 80’s to early 2000’s. I watched it on Comcast on demand around 2003-2006. It was in color.