Are there any laws against teachers attending graduation parties?

I wondering if there any state and federal laws against teachers attending the graduation parties of students because when I graduated from high school, I invited some of my teachers, who a few of came, to my graduation and recently someone told me they don't think that it's legal for them to attend graduation parties. I think that it's okay for them to attend as long as they try not influence the student that the grad party in any way but I want to be sure.