It was level 1-4 where I work up until last year when they changed it to a different grading system. When I started it was just levels 1-3.
Level one would be newly qualified, and two has more experience and can do more on their own. I came in as a level three with about 10 years experience in the US, and truthfully, I regretted it. When I started it was the closest level to management. Level 3s go to court without help. They can have students, and will do most of their work autonomously. They are expected to take a large role in mentoring and assisting the staff and filling in when management is off or too busy. They also tend to get the hairy cases because of their level of experience.
Forgive me, I'm going to be a bit personal. Ignore it all if it doesn't apply. It wasn't the work load I regretted. I was happy to do whatever, but my prior experience was clinical, not child protection, and I had no UK experience with child protection. When they asked me if I felt capable of doing level 3 work, I told them that I didn't know what all that meant, but that I was an experienced social worker with good skills and I believed that as long as I had adequate training and supervision until I was able to learn the ropes, I should be fine.
Unfortunately, I wasn't given any training. My manager quit two weeks in, and I went through a string of managers after that or no management at all. I didn't even have a supervision session until I'd been there for about eight months. I had to guess and figure things out myself. I think I did quite well considering I was thrown into an impossible situation with really terrible management. (not to mention 3/4 of our team on long-term leave, mostly sick leave, because of distress at work). The problem was I was the next closest thing to management (although now there are a few level 4s, which are really managers with caseloads. There are only a few of those, it's a very specialized level).
When the upper management came in, they expected me to be able to run everything myself and to not have to ask questions. I really got set up. In that framework, I could be nothing but a disappointment to them. The upper manager is one of those types who once she makes up her mind, doesn't change it. She then decided I was a problem. She was paying me for near management-level work, but I was working like a regular social worker. It's a long story, but it was very difficult. I think the team struggled as well because shortly after I came, they changed the system, and you had to be promoted into existing spots instead of being promoted by qualifications, so I was keeping social workers with much more child protection experience than myself from moving up in their job, and they were the ones I'd have to go to in order to ask questions if I didn't understand something. Oh yeah, and I was part-time, and I think it's quite difficult to do a caseload of heavy CP work when you are only there a couple days a week. One crisis, and your week is gone and the whole team will have to take your load. I just really started wrong.
So long story short, I personally wish I had started as a level 2. Then I could have just proved myself and moved up rather than having to catch up and be a disappointment. I've regularly been told by colleagues now that I'm a valued part of the team with good skills, but I don't think I'll ever be seen as such by the upper management, and the experience has left me burnt out. I'm always fighting to keep my place. I'll likely be quitting after I return from maternity leave. I've heard of others doing well in management right off the bat, but I believe they had experience doing child protection work already.