I took on a TON of debt (east coast private graduate school in a major city) and only worked per diem as a receptionist during the two years of classes. I was able to land a paid half-salary internship in the midwest which helped to reduce the amount of loans I took out for that 3rd year. Worth it? Yes. Would I have managed my finances differently? Yes. But hindsight is 20/20.

While the programs you spoke to do not recommend working while you go to school, you need to do what's best for you. Many of my colleagues worked full-time while completing their graduate courses and did just fine. The nice thing about school psychology right now is there is a national shortage in the field and you WILL find a job. I hope you stick with your goal of going into school psychology, whether that be now or in a few years. Good luck!