If principals or teachers spread rumors or gossip to about students to other students parents, what laws does that violate and what legal actions can be taken.

Are the things being told, true or false,

If the they are true, they are facts and nothing can be done.

ANY question on law needs to include your general locale as laws vary by area. There may be no laws broken. But there have been more and more laws against bullying that might apply here.

But your first step is to talk to a higher authority in the school district. If teachers are the culprits you talk to the principal. If the principal is included you go to the superintendent or board.