NEED HELP: Big Part of my Plot

All right, so in order to ask my question, I must first explain what I've written so far. Then you might help me from there.
My novel is about an underground school for aliens, wizards, spies, superheroes and monsters. Its called The Universty for Sentient Beings with Incognitos. The new dean of USBI is named Mr. Morial. There are also a branch of other main characters:
Flames Blon is a spy student, though his sister tagged along one day, and so turned into a spy. Once they get home, they hypnotize their mother, allowing them to make her do whatever they want. They make her drive around town for them.
Pandora is studying as both a superhero and a wizard, because of her wizarding powers and her superhero parents. She has found that if she puts yarn into her random-generating backpack, she is able to make sweaters and scarves and such. Well, there's a chance of it being radioactive, but that isn;t the point. She's thinking about starting a fundraiser for the school with it, and perhaps another charity with it.
Henry Penpuffin is a teenage wizarding teacher at USBI, and is in love with Pandora. He begins to help her with her pursuit to advertize her cause.
Finally, Gleise is a kid who decides to hijack a starship at the school's starport and cruises around the city in it with his one and only friend, Smartbot. They crash, run through the forest, find another crashed starship, and Gleise seizes control of the robots there. They happily take him as his leader, except for Smartbot, who had grown his intelligence during the crash, and has not plugged himself into the ship's intlligence system. He then chases Gleise through the forest, the ship as his "body", and captures him.
So my question is: Can you guys think of a way to get Gleise, Penpuffin, Pandora, Flames and Sammie into the school when no one is there? I don't want to explain why quite yet, but can you?
I've thought about making Gleise, Flames and Sammie's stories collide by making the ship start going through the city while they try to tell their mother to stop it. But I'm not sure where it would go from there. So yeah. Please help?

Hm...you certainly have an adventure-laden plot! (The name of your school is great, by the way!) It's going to keep you quite busy-
Wizards, Spies, Superheros Monsters, aliens, mind control,
High-tech equipment like the random-generating backpack, teenage teachers, Starships, other crashed starships, spaceports, robots, robot friends, robot kidnapping (Smartbot, that is)...

With all these different things going on, it might be a little difficult for folks to help out without a little background to give them an idea why your characters need to get into school. What's their goal?

When you say Underground School, do you mean secret? Or do you mean under the ground? (I'm assuming the first, since you have a spaceport...) is this secret school on earth or on a space station (since, again, you have a spaceport- and they'd be harder to hide on earth)

Are the students trying to stop a plot or crime and there are people (or security cameras, or ninjas) that are keeping them out? Is it just locked up and they have to break in?

Are all these students together when they break into the school? Or can they show up one by one, each in their own sneaky way?

It might help if you figure out they normally get to school Can some of them teleport, or do they need space ships? Can the aliens change their look, camoflage themselves or do other nifty tricks? If so, maybe one of the aliens can hitch a ride on the underside of a ship (or truck) going to land at the school, and they can leave an entryway unlocked for the others.

Maybe they put themselves in orbit around the school, disguised as a junk satellite that's going to hit the school and the janitor rounds it up and leaves it in the dump area for the trash ship?

And if you have people that can do mind control, you might just be able to convince someone to take you into the school, under the guise of putting on a play, or packing all those radioactive sweaters for a martian orphan colony.

This is quite an action-packed story...keep going and good luck!

:::It might help if you figure out they normally get to school Can some of them teleport, or do they need space ships?:::

Trying that one again. It should read "It might help if you figure out HOW they normally get to school. Can some of them teleport, or do they need space ships (or maybe special school buses?"

I have one word for you, 'detention'! Most of them have done something that will get them in trouble with the school or if not that can easily be set up. They should have to stay behind after school and write lines. 'I will not steal spaceships' etc. Then your problem would be getting rid of the teacher supervising them. this can be done by: making them get an urgent phone call (parent fell down stairs or something) so they rush off forgetting about the kids. or the teacher suffers from that sleeping disorder where they fall asleep suddenly. or the kids acidentlly knock them out. just a few ideas, hope that helps