Grounds for complaint about my employer (a private tutor)?

I've been looking everywhere and I can't find any answers, so I'd be grateful for any help!

Last term, I got a job at a local private tutor company. It's run by one person, who started tutoring alone, but eventually had so many clients they needed to hire more tutors. Most of the employees are university or college students.

I had the interview, the training (12 hours of it, and a waste of time) but had no contract and more importantly no criminal records check. Nonetheless the boss said they were short-staffed so wanted me to start tutoring before either of these things had been processed -- I could have had convictions involving children, and no one would have known, but still I was expected to do one-to-one tuition with a child (sometimes alone). I never actually paid for the CRB check because I forgot to bring the money, so it hadn't even been started. And as far as they knew, I could have been lying about the money!

Secondly I went through all the training etc, didn't really learn much, we mostly talked about what 'games' to play with the children. Then when I arrived to teach on my first day, the boss started talking about what to do if the children were 'violent'.

I said, 'is [child] likely to get violent?' and the boss acted like I'd asked the stupidest question in the world. Boss said the kids were those who had been excluded from other schools, or who needed 'extra help' or who had come from foster care and didn't have a school place. Some of them, I was told, had been abused and neglected. There was no mention of this in the job description, interview or training at all! If there had been, I wouldn't have taken the job to be honest.

So they essentially wanted me, without a criminal records check, to work with vulnerable children. Children who could possibly be violent, but without warning or training me on how to deal with potential outbursts? When I say child, well my first pupil (who never actually showed up; I never met them in the end) was a teenager and I'm quite a small girl.

I feel like they put me and the pupil in a vulnerable position this way, and it seems this is often how they work. The other tutors didn't seem to think there was a problem. I fear that almost anyone could walk into this job with a dodgy background and be left alone with the pupils.

Do I have grounds for complaint? And if so, who to? I don't think the local authority will deal with it, because it's a private company. I also didn't record anything, other than taking notes, so if it came down to it, it would only be my word against the boss's. But I can't stop thinking about it. Any similar experiences? Thank you for reading!