Resources for determining writing level

[crossmr]

Does anyone have any websites that would help teachers in identifying the level of writing/speaking/etc level of a student in terms of a school student in a western school? Often ESL students are measured in things like beginner, intermediate, etc but many students ask me what their equivalent grade level might be in a western elementary/junior/high school. I can hazard a guess but I'm wondering if there are any tests/marking guidelines that anyone has found online that could be used to evaluate them.

[Tdol]

If you look at the iGCSE exams, they have separate exanms of equal worth, I believe, for native and non-native speakers.
Cambridge IGCSE Subjects

[crossmr]

Thanks. I know there are plenty of tests they can take to get a relative score, general idea of what their level is, but I'm looking more for something I could study that would allow me to look at their work, identify the key things I should look for both included and missing that might help me make a judgment on their writing level.

[Tdol]

It's not simply a test; GCSEs are the public exams taken by 16-year-old students in the UK. These are the international version and they are regarded as qualifications, so, for instance, they are recognised for university entrance and are directly transferable so you can map them in at exactly that point and make a direct comparison with native learners at a specific point in their education.