Automatic expulsion?
As mentioned above, I used to teach at Newton North, one of the most liberal high schools in the United States. Students demonstrating contempt for faculty and staff is a way of life there. Expulsion for locking the door? HA! More likely counseling to find out why the student thought it necessary to prevent the teacher from entering.
I visited Assabet Valley Technical High School a few years back and when I returned to Newton North (NN) I told my students how Assabet had a requirement that all students wear visible IDs. These IDs could be scanned in each classroom at entry/exit and attendance was automatic. Real-time student location was also possible. The NN students declared that they would never wear the ID and that tracking student wherabouts was invasive, demeaning and "unconstitutional", and suggested comparisons with Nazi Germany.
![Roll Eyes [rolleyes] [rolleyes]](/xen/styles/default/xenforo/smilies.vb/042.gif)
(and I use the rolleyes VERY sparingly)
The (much smaller) school where I currently work has been implementing a mandatory ID program this year with mixed results. The technology for scanning is cost prohibitive and the students dislike wearing the ID even under the threat of Detention/Suspension.
School security remains a difficult problem. Perhaps more formal security personel or teachers trained in security measures and specially licensed to carry (Class AAA LTC anyone?) might be the answer.