I've been playing in this campaign for a while and have been in the spotlight quite a few times, but I feel like the DM is prioritizing 2 PCs over mine.  

The group: It fluctuates since this is a high school club, but there's always a minimum of 5 people there; me, the 2 "special" pcs, and 2 of my friends. The DM is a teacher.  We started a few weeks before winter break, and have tried to stick with a schedule of every other week. It started as a level 3 campaign, so we have had about 6-ish sessions.    

For example of my problem: one has an overpowered magic item, and the other was allowed to use a level 5 character from the get go while the rest of the party, me and 3 others, are all at level 3 with no magic items. The DM only narrates one party at a time so whenever the party is split, only 1 group gets the spotlight,and they've split the party several times. The most recent party split is why I've started contemplating leaving the campaign. 

The 2 of them discovered a map to a cave with great treasures and decided not to tell the rest of the party. They left us to go do some business with a village while they go and investigate the cave by themselves. Inside this cave they find an Ice Witch along with an Undead Dragon! They manage to survive this assault somehow, and they find riches beyond measure. Knowing them, they're not going to share a single copper piece of their haul.

My part of the party really wants to enjoy this campaign, but now we just want to leave. Should we leave these 2 players? If I sound like I'm being too entitled how do I stop being like that? I'm happy to share more details if you need them.