I really do appreciate how much effort goes into writing, so my comments are sincerely meant to help you re-write the script. If there is anything which I would strongly focus on its your characters. Audiences will overlook costumes and locations but the characters are the meat of your movie.
The hardest part of filming your own movie is that you have the movie playing in your head while you are writing it. That works well for some. For others, the mental image is more vivid and the script is quite sparse. The trick is transcribing what's in your head into the script. Remember this is the first draft. A good script will go through many revisions. And even when being shot, it will be revised by necessity. The clearer the vision on paper, the easier it is track.
Others forums here might be a good place to find ways of cutting down prop and costume costs. Unless you intend to reuse them, it makes more sense to lease, borrow, or share because ownership will involve storage. But my point was that for a 10 minute short (1 page ~ 1 minute), 2000 pounds sounds a bit high. If you were shooting a 30 minute webisode or festival entry, I'd be more inclined to agree.
My point about the recon house is that it appears only twice each with only a one line delivery. Maybe 8 seconds of screen time. It's a lot of set up for something that is so trivial. One has to ask how much does it really add to the movie?
Code:
INT. HOUSE DAY
The sniper team observe the shooting, GRIFFIN slams his fist
down on the table, angry that they can not do anything, he
picks up his radio and radios in.
GRIFFIN
Sergeant the situation has got
worse.
[CUT TO CLASSROOM]
They could observe the scene from outside the school. Griffin could respond equally well from the situation room. Nothing about this scene requires it to be in the house.
Part of writing is making the scenes relevant and cost effective. I constantly have to think is this scene really necessary? A director/producer needs to think cost and bang-for-the-buck. On a microbudget, you can shoot this in your own house or flat. If you had to pay for a site, you might think that 8 second shot isn't worth the expense. Trust me, these are lessons that we all learn. I had a director tell me to change a location because it is too expensive to shoot. (I had to cut a whole scene and re-write parts of the script to accommodate the change--draft 6, revision 4! ugh!)
As an aside, your script would benefit from being broken into visual shots.
Code:
INT. HOUSE DAY
Griffin stands at the window with binoculars to his eyes.
A gunshot rings out.
He lowers them as his eyes close and his face grimaces.
He slams his fist down on the table before picking up the
radio mouth piece.
GRIFFIN
(to handset)
Sergeant, we have a casualty.
In contrasting the two, you need to show that he's angry and frustrated, not tell us. The audience can't see that. These are separated as distinct shots or descriptions. As a director, I can see in my mind a close up shot of Griffin. Hear the gunshot. Then a medium shot where he reacts to what he's seen. The director can tell the other actors how they should respond in the background. I also changed it to "we have a casualty". They've had a 'situation' and it 'got worse' doesn't really convey anything. If I had Charlie and the tutor being threatened before I cut to this scene, there is some ambiguity as to who was shot. It might have even been a terrorist or another student. Then when we switch back to the classroom, we learn it was Charlie. Part of the drama is not laying out all the cards immediately.
The first draft is to get the concept on paper. Then comes the hard part of being ruthless in your revision--do I need this scene? this character? Would they really talk that way? that long? Should something be happening now? The secret to writing is re-writing. The shorter your film, the easier it is to shoot when you have few locations.
As a writer, I always describe my main characters. It lets the person reading my script know how I see them and conveys how they will act. Typically the director and casting director will see a different person or have an actor under contract who must fill the role. But for me, as a writer, it helps provide a continuity. The amount of description is dependent on their importance to the story. Again, the script is a blueprint. It can be changed after the fact, but you need to be clear with your vision when you first start. A clear character description helps your actors. It helps to know who is older/experienced or young/naive. Who is strong/defiant and vulnerable/submissive. These are developed by description, action, and dialogue.
Don't just say someone is a scumbag, show it. Currently the terrorists basically stand around waiting. That doesn't sound very clever or intentional. They targeted the school and this class intentionally--why? As a writer you need to help the audience piece together why. Is Katie's mom/dad a high level operative? Did s/he go missing? Is that why she's fragile? You want to have your characters' lives present your story.
Thinking through the timing is critical. The SAS couldn't know this was happening in advance or they would have stopped it. Have the terrorists send the tutor out with demands. This brings in the police (Alan). In turn, the police pull in the SAS. Now the SAS can be more fully active. Or if you want to play that the SAS were in the know, then make the tutor an SAS plant and play with that a bit. You need to have a way for the police to become involved. At the moment your story starts no one could possibly know that the classroom has been taken. You tip your hand by starting with the SAS. It would be more powerful to have Henderson alerted and demand information about these three terrorists after the fact. Maybe another teacher enters unaware and is told to evacuate the school. Or maybe have the terrorists pull the fire alarm. The timing needs to seem realistic. Ask yourself "How would someone know about this? Then what?" The more reality-based your movie, the more credible it has to be.
It may sound like a lot of work, and it can be. However, for a short, the emotional drama could all play out in the classroom with brief cameos in the situation room if you want. Two locations help focus development and provide the build up, drama, and resolution.
In the end film the classroom being gassed. You need only a few standard military costumes and one gas mask. The power of your story will be in the portrayal. And rather than make the terrorists the bad guys--a rather flat portrayal--introduce their lives. Why would they resort to storming a classroom? This is the difference between 2D and 3D characters. Most new writers develop their heroes but not their villains to their detriment. Just as you play with lighting and sound to bring out the visual and mood elements of a scene, use your action, description and dialogue to bring out the nuances of your characters.
Again, I am not saying your work is horrid or you are a bad writer. These are areas which we all stumble against. Thank you for taking my comments as they are intended--to help enhance your effort. With thought and effort, I think you can have an excellent short. Good luck with your shoot.