Nope. Pretty much 100% of schools in the U.S. (with internet access) operate a transparent or explicit HTTP(s) proxy as the only way out to the internet from student-accessible vlans. Websense is probably the most popular commercial solution. My school district ran a Squid extension called Squidguard for a long time before switching to the filtering solution bundled with its new wireless controller system.
Implementing web filtering is a condition of receiving federal subsidies; they take it seriously. A school with only a handful of PCs might use a host-based solution but proxy-as-the-only-way-out network design is very, very common.
Implementing web filtering is a condition of receiving federal subsidies; they take it seriously. A school with only a handful of PCs might use a host-based solution but proxy-as-the-only-way-out network design is very, very common.