Well, Twilight was still just a foal when she hatched Spike. So how could have she have been ready to raise a child back then?

“All you did is hatched me.”

@Xonxt  
To see how the prospective student deals with or handles failure or inability to complete a task far beyond their capabilities. You can gauge much more about someone by seeing how they fail than how they succeed.

@MadVillan  
Maybe there is more than just that test. It’s just that Celestia was so impressed she didn’t need to or someshit like that.
 
Maybe the parents need to sign some sort of agreement beforehand. But that’s stretching it.
 
The writers probably never gave a shit about it, anyway.

@Hebbocake  
But it’s a magical school, and that’s it’s admission test. How would they actually determine their magical capabilities? Also wouldn’t everyone catch on and parents just tell them about the test?

@Xonxt  
My Spike headcanon is similar, except his egg wasn’t inert: When Celestia obtained it centuries ago, she put an Age spell upon it to keep it from hatching. When Twilight got her magic surge, she canceled the Age spell so thoroughly that not only did Spike hatch, he grew up to the size he should’ve been as a centuries-old dragon. Celestia had to re-apply the spell and “dial back” Spike to a hatchling to avoid raising suspicions.

Tru story

@MadVillan  
To see how the students would cope with loss of this big amount.

@Xonxt  
So an impossible test then, what would be the point of it then?

@MadVillan  
I kinda had this weird headcanon, where that egg that Twilight was given at the exam was actually in the school’s possession for decades, if not centuries, and was considered dead/empty/petrified/whatever. And Twilight, having had her powerful magic surge, somehow revived and quickened the egg, incubated it and hatched it, all in matter of seconds, effectively becoming Spike’s biological/magical mother.
 
But the showrunners most likely never thought about something like that or even thought about Spike’s origins at all, because the stall clearly doesn’t care about him and only uses him as a comic relief slash punching bag slash occasional straight-man.

Well she didn’t lay the egg she just hatched it, for a test and not out of any desire to raise him.

@neo4812  

i would love to see an ep where spikes real parents come and try and take him away, or atleast the mother or maybe one of spikes siblings comes into town and wants him to meet his family and we learn more about spikes unique species of dragon and why they don’t have wings like other dragons