I can't say whether or not punk is dead. As a matter of opinion, I really hope not. If your students have no idea where to begin with punk, this particular entry could serve as a most basic primer.
Punk music is often lumped under the larger heading of rock music, but it had its roots in the 1970s in New York City and London. While early punk bands went on to experiment with various styles of music (e.g. Talking Heads, Blondie), the more stylistically straightforward punk bands that developed in the 1980s (Dead Kennedys et. al.) have come to define the style for past 30 years. Punk has mutated over the years into various smaller facets, including hardcore (Minor Threat), riot grrrrrl (Bikini Kill), and the more commercially palatable pop-punk (Sum 41), but many aspiring musicians have sought to imitate the style and work ethic of early punk rockers (e.g. Black Flag founding member Greg Ginn claimed the band would rehearse up to 16 hours a day). Punk rock often refers to a sort of DIY, anti-authoritarian ethos as well as a musical genre.
Stylistic traits: punk rock was always intended to sound rough, unrefined, and under-produced. Most punk bands use the most basic instrumentation, with many punk bands only consisting of three members. Song are often played at a very fast tempo and include a great deal of emphasis on beats 2 & 4. Drumbeats are largely very simple and unadorned, except for the occasional super-fast fill. Punk songs are also mostly very short and vocals are often shouted in a confrontational manner. Many of the chord progressions reveal a strong influence of blues-based guitars, simply played at breakneck speed. In its early years, punk rock was deeply influenced by reggae music (e.g. The Clash).
Instrumentation: guitar/bass/drumset, intending to keep the music making process simple.
Lyrical consideration: subjects often include politics, general musings on life, absurdities (e.g. The Descendents "I Wanna Be a Bear"), anti-authority messages, and almost never about love. Profanity tends to be rampant in punk music, as does discussion of drugs and substance abuse. Many punk lyrics are written with the intent to shock.