Working with special needs children

I started my new job as a sub-paraprofessional today. Basically they post jobs on a system with NO description, only a schedule and a school name. They don’t ask for a resume or anything. I was given a special needs child right off the bat. I have no experience with children in a school setting, let alone special needs children. When the teacher/staff was told about what child I was there to care for, they all laughed. This child was hitting other kids, biting, screaming. He does hit adults and he has ran off the premise twice (I was told). All of the students I cared for today were special needs. Some had behavioral issues, some had autism, some had visual impairments. I am just not qualified AT ALL to be working with these children. I don’t know how to give them the proper care that they need. I don’t know what works for them. I basically felt useless and the other paras had to help me out a lot. My fiancé thinks that I should stick with it and see it though but the assignment is a month long. He said I shouldn’t want to be seen as a “quitter”. And my friend thinks that I need experience first to be able to work with these children. We’re both shocked that I didn’t need a certain certificate to work with them, they just threw me in. When I was leaving, they all asked me if I was going to return. They said that the others usually run away. Since I said that I would go again tomorrow, I will, but I’m not sure if I should stick with this assignment. I know that if I don’t, my fiancé would be really mad. I can get a new assignment the same day it’s posted so it’s not a matter of being unemployed if I don’t continue, he just says that I leave jobs too quick which I don’t agree with. If I stay and I’m not helping, I’m really doing everyone a disservice.