1. The whole story is a recollection told from Twilight’s point of view, so obviously we’re not going to see anything Twilight didn’t personally witness, particularly Celestia’s thoughts. Judging by her frequent nervous/worried looks throughout the tea party, though, she does seem to be coming to the realization that maybe Twilight can’t handle the responsibility yet.
    
2. Celestia does indeed state that Twilight would only be helping with “the dragon” when she didn’t have time. Of course due to #1, we only see the times that Twilight has him.
    
3. It was impressed on us as fans early in the show, from the very first episode even, that Twilight is obsessive when it comes to her assignments, often even unhealthily. I wouldn’t be surprised if Twilight actually only had Spike for a couple of hours per week, and she spent the remainder of the time fretting over how best to raise him–reading books on reptile biology, books on pony child-rearing, compiling and reviewing her own notes, speaking with doctors, veterinarians, zookeepers, etc., while neglecting her magic studies. As this was a direct assignment from Celestia herself, she’d see it as a more important task than the rest of her studies.
    
4. Actually having to take Spike to class is pretty absurd and this is my main problem with the issue. Having a child in class is going to ruin the learning environment not just for Twilight, but for everyone else as well. It’s possible this only happened a few times as the comic only shows (IIRC) two occasions. Also, since this is Twilight’s recollection of the events, she’s going to remember & mention the worst she had to deal with.
    
5. Spike’s already saying his first words and crawling around after only 2-3 months (this all took place during the first semester, right?). That’s some pretty fast development considering the time between Twilight’s exam/Spike’s hatching and Twilight’s first day was a couple of months at most. Speculating here but by the time he’s 1 year old, he may be as mobile and active as a 3 or 4 year old human and able to entertain himself while Twilight studies (or follow along with her). Given Twilight’s penchant for thinking out loud, it would make sense for Spike to learn as she does. That might explain his education - accidental homeschooling.
    
6. Twilight’s conclusion - that Celestia wanted to give her a friend - is her own interpretation, not necessarily Celestia’s intent.
    
7. The art is absolutely glorious.
    
   I’d give it a 3/4, mainly for the absurdity of taking a baby to class. One line from Twilight, something like “When I look back on it, I probably only had to care for him a few hours a week that first year, but it seemed like an eternity.” would have upgraded it to 3.5/4. Celestia’s actions - while we like to question the wisdom of them sometimes - are not inconsistent with the show so I’m not going to penalize it for that.
    
   The story gave me some food for thought - that Spike may have developed so quickly that he was able to learn alongside Twilight in her own studies. Maybe not at full capacity, but at least picking things up here and there. After all, Celestia’s School seems to cover everything from “Magic Kindergarden” all the way to college-level education. By the time Spike is 4 or 5, he’s basically independent and maybe even able to help Twilight in her own studies, much as he does at the start of the show.
    
   This also lends some credence to the idea that as a dragon, Spike is more mature than his chronological age would imply when compared to ponies. He does seem to be more independent and responsible (usually) than his peers like the CMC.

@Gungelion

Welp, Celestia made another one snap

If you want to make an omelet…

Welp, Celestia made another one snap