I was hired as a behavior instructor almost 6 months ago. Upon being hired I was given a "full-time" position, meaning 20 hours per week (per company standard). Consistenly I have not been given 20 hours per week as PROMISED and have voiced my concern over this. Its always, "we are working on it, be patient yadyada". What options do I have here besides search for employment elsewhere?

Keep complaining, if they consider 20 hires full time ( I know of no where that does that the less amount I have ever heard of was 32 and many 35) so I will assume they allowed you benefits.

But unless there is a written contract to provide you 20 hours they will schedule you the hours available for that job.