This is an example of how one school system gives grades to newcomers.
http://lcsokcps.weebly.com/uploads/1/7/8/5/17851241/mainstream_companion.pdf
How can I give my students grades?
Math, Science, and Social Studies
Content should be taught using modifications for ELLs, and ELLs should be provided multiple methods of demonstrating what they have learned, other than a standard assessment. The goal is for ELL students to learn the same content as peers (not watered down), but with simpler language. First year newcomer students should be assessed according to Level 1 of the Can-Do Descriptors:
Grades 1-2, Grades 3-5, Grades 6-8 https://www.wida.us/standards/CAN_DOs/
For example, according to the Can-Do Descriptors, a Level 1 student can label a picture. This might be a good assessment of a science concept. Creating a timeline with simple labels (words or phrases) would be a good way to illustrate some Social Studies concepts.
Language Arts and Spelling
Tons of good strategies for working with newcomers, content assessments, grading, etc.
Grading Newcomers: A Can-Do Approach (Using WIDA Can-Do Descriptors https://wida.wisc.edu/teach/can-do/descriptors to Grade Newcomers) https://inspiringenglishlanguagelearners.weebly.com/blog/lets-go-a-step-further-with-can-do-descriptors