[[WMG: Sid will grow up to be his world's BillNyeTheScienceGuy.]]
Hey, why not?

[[WMG: Unbeknownst to Sid, his parents are obscenely rich.]]
* Sid's parents don't let him know about their filthy rich status so that he'll have a relatively normal childhood. They even go so far as to pretend to have mundane jobs just so that Sid won't have a clue about their mind-bogglingly immense wealth.
** However, they did splurge a bit on their house and yard, which seem really huge for a supposedly middle-class family. Also, the interior of their home seems pretty sleek and they have up-to-date technology, such as rather modern-looking refrigerator.
* Sid's parents fund Teacher Susie's school.
** That explains how the school can survive financially with only four students.
** It also explains why Sid always gets to choose the topic of the day; and it provides a reasonable explanation for why the other kids (who are presumably nowhere near as rich) are obligated to do a little song and dance when Sid arrives each morning.

[[WMG: They live in a post-apocalyptic world]]
Because they live on a house-lined street with no one else there. Maybe they were some doomsday cult who managed to save themselves, but it explains why only those families go to such a well-stocked school with only four kids - their parents are our reaping all the food and goods now sitting around. Every day the kids through the motions of regular life.

[[WMG: The kids are actually in a special ed class.]]
This could be an explanation on why there are only four students for besides the age they are at a special education class tends to have less students in it.

[[WMG: Sid and his friends attend an exclusive private school.]]
Goes back to Sid's parents being rich, but maybe the other kids' parents are too. Not the most exciting of theories, but it would explain why there are only four in the class.

[[WMG: The whole science thing is a distraction. Sid and his friends are the next Music/TheyMightBeGiants.]]
With a focus on science-based songs. For scientists, they sure do spend a lot of time singing. And they're pretty good at it too.

[[WMG: Gerald is secretly a ninja.]]
* In one episode, Gerald was sneaking around inside the school during rug time, and he (very clearly) hid behind a bunch of blocks before immediately appearing on the other side of the room. He was suddenly right next to everyone else on the rug, as if he were there the whole time! Even Teacher Susie looked genuinely surprised.
** It should also be noted that during "The Dirt on Dirt" episode, the kids were about to play pretend, with Gerald pretending to be the Earth. Keep in mind that May was the only one who knew beforehand that it was Earth Day, while everyone else (minus Susie) found out at rug time. Well, Gerald leaves for not even a couple of minutes to go get something from outside somewhere, and comes right back with a gigantic Earth-shaped hat! How did he get that so quickly?! Coincidence? I think not!
** This would explain why Gerald acts so darn goofy all the time during the day, as no one would suspect him to be a serious ninja at night. This could open doors for a potential spin-off series for Gerald.
** Not only that, but Gerald has been known to just generally startle characters, especially Sid, on numerous occasions.