i'll tell you walkthrough and achivements
1.Get out of the classroom then take the fire extinguisher.Then go the the next room you'll see that talking to you and kicked you out of the room.
2.Go the the next room which you'll find a gun on the table take it and go to the previous room and kill Alcucard.
3.After you kill Alcucard take the key and do not leave the room yet, shoot the tables which protects him and then shoot him and you'll get overkill achivement
4.Get out of the room and move to the left until you'll find a a gut holding a gum (i dont remember his name) do not talk to him just shoot him i think shoot him 3 or 4 times you'll get achivement you'll get brutal achivement then take the key. 5.And then go inside the boys toilet tap the water you'll get tap that achivement,then you click on the cubicle's handle click on it several times you'll get Marc Summers achivement then click on the door beside the cubicle you find a guy at asking you to close the door well ignore him and just continue the words his saying until you'll get scat man achivement then get out of the boys toilet and go inside the girls toilet you'll find a ninja which you have to fight him when you are fighting him just follow the red line until he dies.
6. After you beat him take his gogles and then leave the room on the right you find a light green colour locker open it and use it you'll get health. Then go to the left keep going to left and you'll find a room go inside and use your fire extinguisher you cannot enter the room yet so leave the room go back to the classroom and use the ninja's gogles use it and you'll find key take it and go back to the door that a locked.
7. When you started battling cassandra do not kill him first, shoot the big barrel near cassandra and you'll get BruckHeimer achivement then finally you can kill him and you won you got the Save the day achivement.
I really had fun in this game well good job dude this is way easy for me -_-'' so anyways W00T!