To get a job at a bank you need to have a high school diploma or GED and possibly a degree in something for some positions at the bank.
Usually a bank teller only needs a high school diploma or GED but other positions might require a college degree.
A 2-year associate or 4-year bachelors degree can help you get hired faster than not having the degree but it's usually not necessary.
Make sure you're good at math and then write out a good resume and when you write your resume make sure to list all your good qualifications and call back for the bank job if you're not hearing back from them.
Calling the job you're applying for is a good way to get a job because it shows you're interested in it.