looking for new campaign ideas to start a group through my school, DMing for the first time, can I get some tips and tricks and some ideas?

evil crabs.

gobiln invasion.

yuan-ti(snake people) have taken over the governement

evil king

any long fairy tale

demonic incursion

kill a dragon

evil necromancer is raising the bodies of dead ANIMALS and the final boss is the undead tarrasque

get a dragon to kill a bigger threat

a mysterious fortune teller is making their predictions come true

a fey creature, incarnate in the from of a small child is slowly corrupting the city and if it succeeds, the city will be trapped in the feywild forever!

ghosts.

something is killing the harmless spirits that reside in a village

zombies are forming their own sociecty, the only problem is, it's right on the borders of the kingdom

far realm incursion

celestials have been corrupted by the far realm and the players have to side with feinds to stop them

Ask your players at session 0. When the whole group brainstorms an idea, everyone will be more invested in it. Though having a couple ideas to seed the conversation can be helpful. The above poster gave some decent options there. 

I had a side plot in my last campaign where I wizard was trying to find the secret keys to an ancient tower that was supposedly filled with the preserved knowledge of a lost situation. 

In order to do that, he had to try summoning angels, devils, and other entities who's names are mentioned in historical accounts as having been summoned by the ancients, to get information about the keys' resting place. 

In order to do THAT, he will need a LOT of silver and gemstones as materials for his summoning rituals. He's a practical wizard (not necessarily evil, he believes he's working ultimately to forward progress), and thus he's contacted an army of hobgoblin mercenaries and has set up shop in the southern part of a less-defended barony, taking over towns and raiding them of all valuables, imprisoning villagers for experimentation and workforce, and is threatening an entire area from the ruined fortress he's moved into. 

The players are working with the largest town in the area and where refugees from the other villages have flocked to, and have various goals to achieve in order to prevent the last bastion from falling. 

Quote from TylerTheCreator777 >>

looking for new campaign ideas to start a group through my school, DMing for the first time, can I get some tips and tricks and some ideas?

 If you're a first time DM, with presumably inexperienced players, you could do a lot worse than just pick up the Starter Kit or Essentials Kit and just run the campaign that comes with them. They're good introductions to the rules and offer simple but enjoyable short campaigns. Also if it's a school group ask one of the teachers to contact D&D Beyond about the educators kit (here's the details https://dnd.wizards.com/resources/educators) which will give you a lot of stuff for free either digitally or physically depending which country you're in

If you're after something which can kick-start a campaign, then I recommend the Steepfield Cheese Chase - I know it's my own work and all, but I'm currently DMing a 2-year 48-session game which was spawned from it. It's in my DM's Guild Release Thread.

Otherwise, I definitely recommend that you discuss with your players what they want from a campaign. Ask them if anyone has any ideas for their characters and their backstories, and see what pieces you can fit together. One person says "I want to fight a dragon!" and another says "I'm on the run from a mob boss", then boom, mob boss is a polymorphed dragon, trying to get revenge for whatever happened. They do side quests whilst fighting off the mob, until a rival mob offers them a chance to deal with the mob boss chasing them. By now they're all annoyed, and nobody knows they're a dragon, so they go for the infiltrate-assassinate approach. Big reveal - now you're fighting a dragon!