Questions

I was hired for $15 in my industry. They gave me a chance w no experience. In my last job i was hired for $12 I was happy w $15 and didn't know any better. I have been on the job for 3.5 years. No raise in that time... I finally decide it is time to ask for a raise. I do my research and see the company avg is already $21 an hour. I politely request a meeting for a salary adjustment. My boss tells me it will have to wait.

In my 3.5 years I have improved every year, I have taken on new responsibilities. I have helped train new hires. I am helping a new hire and say , what the heck, ill ask what she is making. She tells me she is starting at $22 an hour. Here I am training her at $15. She has no experience and frankly, looks like she won't be good at the job. No complaints. I politely explain to my boss that I would really like to consider a salary adjustment.
He tells me that it is unlikely and they probably won't raise my salary past the usual 5% no matter what phrase I want to use. That is about a 35c raise.
I feel completely disrespected and underappreciated. Im training someone who can't write complete sentences and she is making so much more than me. I am now struggling with what my next option is. Do I leave or stick it out?

It's frustrating because I have serious credit card debt outside of school (and I'm currently working a job to pay that off and afford to even go to school) and I'm a STEM major where it requires serious life dedication to even get good grades on important classes. For the past couple of years, I've been getting mostly Cs because I never have enough time to put more work and effort to do better due to work and occasional family problems. It sure as hell doesn't help that a C hurts your GPA, which makes it extremely difficult to get any internships that demand at least a 3.0 minimum.