What formative assessment method would help Ms. Salas assess her ELLs' math skills effectively?

Using spot-checking during group work allows Ms. Salas to assess her ELLs' math skills in a dynamic and supportive environment. This method enables her to observe students as they collaborate, providing real-time insights into their understanding of mathematical concepts and language use. Spot-checking can also help identify specific areas where students may be struggling, allowing for immediate feedback and targeted instruction.

This approach is particularly effective for ELLs, as it offers opportunities for authentic communication and interaction among peers. It also fosters a less intimidating atmosphere compared to formal assessments, encouraging students to express their thoughts and reasoning without the added pressure of strict time limits or the language barriers present in standardized tests. By observing students during group work, Ms. Salas can tailor her teaching strategies to better meet the diverse needs of her students, promoting a more inclusive learning environment.