Spoilers are ahead, but marked with the spoiler tag. I would recommend you play through the game first and then clean up your achievements, but to each their own. If you have any questions, please comment below!

These achievements are unmissable while playing through the game.

Prologue: Finish the Prologue.
Unlocked when Kenny tries to escape the basement and dies.


Class Over: Leave the Office Building.
Unlocked after meeting the teacher in the attic and leaving the office.


In My Office: Find the Principal.
Unlocked after opening the safe through solving the compass puzzle.


Research: Explore the Library.
Unlocked after finding the Principal in the Library.


First Aid: Go to the Nurse's Office.
Unlocked after finding the Nurse in her office.


Private Screening: Search the Auditorium.
Unlocked after playing "Reel 23" on the projector in the Auditorium.


Detention: Search the Basement.
Unlocked after being captured and placed in cells while exploring the Basement.


Investigation: Check out the Dorms.
Unlocked after dropping the coffer down the flue in the Dorms.


Hall Pass: Enter the Gardens.
Unlocked after entering through the gate to the Gardens.


A Stroll in the Dark: Cross the Gardens.
Unlocked after finding the statue in the Garden and exiting.


The End: Finish the Game.



Honor Student: Finish the Game on Normal.



With Distinction: Finish the Game on Hard.



Magna Laude: Finish the Game on Special.


You can get the last two done on the same run. Just play "Special" on the "Hard" difficulty.

These achievements are missable. You will most likely get some of these by chance throughout playing, but I've listed out valuable information for completing them. Spoilers below!



Present!: Every Playable Character Survived at Leafmore.


Strategies

Since you can only control two characters at any time, it makes the difficulty of this achievement drastically easier.

As you get discs throughout playing, be sure to save whenever you feel you might fight a group of enemies. I recommend playing on the easiest difficulty for this, as your chances of dying will be substantially lowered.

Be sure to search for energy drinks and health kits, as they will be your saving grace for most of this achievement. I would advise letting your partner carry the heavier ordinance (shotgun, laser), as these things have more damage and therefore more protection for the AI.

At the end of the game, you're going to fight the final boss. All of your characters will group together before the fight happens so make sure to do this to ensure everyone stays alive:

• Make sure to tell the AI to "Stay Here".
  
• Make sure to trade all of the AI's weapons over to yourself.
  
• Be sure to check Walden's Bag near the entrance on the left for ammo and health.

Boss Strategy

Fairly easy fight, you just have to kill all the tentacles.

There are five in total and don't have much health, but be wary of a couple of things:

• Standing in the pool the boss is in will damage you the more you linger in it.
  
• Watch the ground for circles. Liquid fires up through it and will damage you if you're on it.
  
• The laser is the best against this enemy, I would recommend saving it until you fight him.

Important: When you kill a tentacle, a light will spawn near it. Stand in it immediately! (Let the big darkness attack go through, then resume fighting tentacles. Do this after every single one.



Three with One Blow: Kill 3 monsters with a single light grenade.

Strategies

The easiest way to get this is at the Garden when you're obtaining the statue. If you have a light grenade with you, an ambush will appear once you've grabbed the statue from the podium. Throw the light grenade following that and you should kill several enemies, netting you an easy achievement. (Credit: EzequielV)

Another way is with a specific hallway near the end of the game.

After you place the four statues on their respective podiums, you'll need a lever to activate them. When you enter the door on your left, you will find a long hallway. At the end of this hallway is a light grenade.

Three enemies will quickly come to get you once you reach the end of the hall, but you can throw the light grenade towards them and unlock the achievement easily.





Heavily Armed: Find all the weapons.


As far as I understand, you do not need to collect variations of the same weapon. I got the achievement with just these weapons. Here is the list as well as the locations where you can find them.

Baseball Bat: Found on the table after the Prologue.

Metal Bar: Found in the attic after Mr. Walden drops it.

Automatic Pistol :Found in Friedman's Office in the Safe.

Old Pistol: Found in the janitor's closet of the classroom building.

Old Shotgun: Found in the janitor's room (not closet, which is in the classroom building.)

Revolver: Found on the upper floor of the Library in the left room on a table.

Two Barrel Shotgun: Found in the garden in the small shack. It'll be up on the roof, so just use a melee weapon and strike the wall at the back of the shack and it'll fall.

Light Grenade: Found in the underground secret lab.

Laser Gun: You can find it in the room in Friedman's lab where you find a photo of a student who underwent mutation, there is a cage you can push to reveal a hidden room with a ceiling monster and the laser gun in the bench. (Credit: EzequielV)

These are the only ones that I needed to complete the achievement. You do not need to get any of the extra weapons the become available after beating the game on various difficulties. This list seems to do the trick.



Trigger Happy: Kill 150 monsters with a firearm.


Strategies

You can save your game before points you know will have enemies then save immediately after to have it count towards the achievement.

I recommend using two save discs. Use the first one after entering the code to the Garden. Enter the Garden and you should be able to kill up to ten enemies, give or take. After you've successfully killed the all, exit the Garden on the opposite side and save your game.

Kills will count if you don't save, but the number tends to be lower than what you actually killed. Saving makes sure that you get all the kills. If your achievement count is rising, close out of your game and let it sync with Steam Cloud.

If you are playing on Special Easy, you can use the pistol you find in the Janitors Closet when you travel to the Classroom building at the beginning of the game. In the Science room at the end of the hall, there should be seven enemies. Save after getting the gun, shoot the seven, then save after.

Reload save and repeat.




Brutal Achievement: Kill 50 monsters hand-to-hand.

You can use all melee weapons for this achievement.

You can also use the same trick for the Trigger Happy achievement, although I recommend that you save in an earlier part of the game because it becomes substantially harder to melee enemies during the end-game.

If you are doing a Special run for the higher difficulty achievement, you will get something called a Morgenstern Bat. The damage on this weapon is as high as an old pistol and will easily net you the achievement if you use it during early game.

If you are playing on Special Easy, you can simply save before entering the Science class at the Classroom building. Use your Morgenstern Bat on the seven small enemies in the room, save your game afterwards, then reload until you get the fifty you need.