Would It Be Illegal For An Employer To Not Pay A Stipend That Was Promised Verbally And In Email But Not Clearly Outlined In The Contract?

Location: Arkansas, employer in Fayetteville

Employment Details: Public Charter School employee, first year in this system and state

Contract Outlines: 50,000 salary for teaching position (lists my position here). Underneath it reads-

Stipend: "See salary calculation and additional compensation table for details"

Nowhere in the actual contract does it list the name of which stipend I was promised or am eligible for (band coach/club stipend). I reached out to HR to inquire this, and was told it is additional pay and paid as two payments that are basically bonuses throughout the year and not with the salary which is why it wasn't included in the contract. I thought this was acceptable and needed to sign the contract to get the job so I signed.

I have been having communication issues with the district regarding the actual qualifications for getting this stipend because my principal keeps telling me I need a certain number of hours to get the stipend but there is no clearly defined district policy. I reached out to HR again to clarify, and they basically said it is up to the principal. After talking with a coworker, she said last year she was promised a stipend that was actually IN HER CONTRACT and they didnt pay her until she threatened legal action. I know she had a right because it was in her contract. If i am in a similar situation but it wasn't in my contract or clearly defined, am I screwed?​​

Asking so I can try and request an amendment or addendum to the contract ASAP to try and avoid any suspected issues. Overall this whole district is very disorganized and I have decided I will not be returning after this school year is done.