Thanks to a Supreme Court ruling and a federal law, public school authorities find it difficult to get rid of disruptive students or even those exhibiting criminal behavior.

• In Goss vs. Lopez, the U.S. Supreme Court ruled in 1975 that a state must protect a student's right of access to a public education -- including students guilty of criminal violence.

• The Individuals with Disabilities Education Act passed by Congress the same year bars public school officials from suspending disabled students for more than two five-day periods in a given school year without the permission of a judge or the child's parents.

• Schools must guarantee a "free, appropriate public education" for any learning-disabled student who is expelled for any reason.

Teachers complain that the label "learning-disabled" can be applied to students who are little more than criminals reclassified under another name. A regular student who brings a deadly weapon to class would often be expelled for a year; but one classified as "learning-disabled" would get at most a 45 day suspension.

Experts say that the best teachers try to avoid teaching at dangerous schools. Texas, Arkansas, Minnesota and other states have started programs to establish separate schools for expelled students.