I've got everything unlocked just needing a few more things to complete. The House Crest finder arrow shows the crest piece to be on the top level but i can't find a way up to it. any ideas anyone? Cheers
Year 2 - Chapter 5: After flying over the water, build the ramp on the pier, stand on the end of it, and cast reducto on the large gate. Some frogs come out, which you can ride on. There are some gates made of vines that come out of the water that you have to ride it through. Once you've gone through all of them, you get the crest.
Year 3 - Chapter 5: I can't remember which one is the Slytherin piece, but judging from your first one, it might be the one where you ride a frog through checkpoints (I didn't know about these my first time through either).
Year 4 - Chapter 3: I can't give you the exact one, but when you're running away from the dragon in the halls, shoot at the wardrobes on the sides of the hall, one of them has the student if I recall correctly.
Year 4 - Chapter 6: I believe this one is in the area with the sphinx that you lure a spider to. I think the kid is straight across from it, as far down as you can go, being restrained by vines. Use the lumos spell (projectile one) on it.
Hope this helps, and sorry if I'm not 100% accurate with locations, but I know I've got the actions right.