First off, I loved it. It felt really personal and had a story to piece together. I liked the settings, the effects, and how they tied into what was going on. The beginning was solid, I loved the part where you followed the other character but couldn't keep up. It really set the mood and feeling of the game. The vanishing effect and school bell were cool touches and the way you let the player decide where to go gives a bit of mystery as to whether or not you've explored everything. For example, next to the stairwell room there's a white structure you can clip the camera through to see that looked really cool but we never get to go to!
Some of the areas did remind me a bit too closely of levels/areas from The Beginner's Guide, a game I'd highly recommend playing as it's right up your alley. But keep in mind people online can be pretty mean if they think you're copying or using an idea without the original context.
With stairs, use a plane or flat collider so the player camera can glide up and down smoothly. Also, don't use the Unity car model, it cheapened the look of the area and most people know where it's from. Plus, a futuristic car didn't make any sense there. I'd buy you a $10 car model in a heartbeat just so you didn't put the Unity car there hahah.
But great job and congrats man!! I hope to see more from you in the future! :)