School Bus Kidnapping

[Ash]

I remember a film that came out either in the late 80's or early 90's which was about a group of kids and teachers on a class trip in a school bus. 
They break down (I think) and are taken prisoner by a group of psychotic men.
The men take them to some rural region and torture, kill and generally scare the hell out of them.
I seem to remember a teacher being chained to a tree.

One of the teachers manages to kill several of her captors.  (not 100% on that)

I'm pretty sure this was either an Australian or British film production because I remember the actors all having non-American accents.
And I think it was a made for HBO, Showtime or Cinemax film.

Anyone?

[Doc Daneeka]

Perhaps it was the 1986 FORTRESS with lesser commando Vernon Wells? I'm afraid I don't believe it's available anywhere.

[RapscallionJones]

Depending on your DVD playability options, there's an R1 of this available.http://www.amazon.com/Fortress-Sean-Garlick/dp/B000GAKDP6/ref=pd_bbs_sr_1/002-1757668-9704054?ie=UTF8&s=dvd&qid=1189794414&sr=1-1

[Doc Daneeka]

How new is that? I think I remember looking for this one before and I couldn't even find a VHS!

[Ash]

It was Fortress!

Boy, that film is older than I thought.
For some reason I kept thinking it was made in the very late 80's or early 90's.
I'd forgotten that it was released in 1986.

Thanks for the help.
One karma for you!  

[Mr. DS]

I think I used to catch this one a lot on tv.  Isn't this the one where the kids and teacher have to swim in an underwater cave to escape or something?

[Ash]

I think I used to catch this one a lot on tv.  Isn't this the one where the kids and teacher have to swim in an underwater cave to escape or something?

Yep...
That's the one.