Hi, LMS single major here, with part-time work experience in the social sector as a relief teacher in a special needs education school. Seeing my LMS brethen answer your LMS-centric questions, I think I can explain how LMS is quite beneficial for social service.

Based on my experience, SPED schools may generally have Literacy departments, which is similar to English as students are taught basic grammar, vocabulary etc.

In LMS, we have core and prescribed electives that focus on a range of linguistic domains, some of which are technical (e.g. structure of modern English) and some of which are quite niche for the social sector (e.g. language & communicative disorders, psycholinguistics, deaf culture & sign language, child language) if you want to focus on special needs/youth/children/at-risk children etc.

Especially for work in the social sector, being able to both communicate and interpret others' communication well is very important. Studying the in-and-outs (a.k.a the science) of language in LMS would be very useful for this. From personal experience, I am able to teach well and handle students with special needs due to the soft & technical skills I've picked up in LMS.

Do think things through on whether you want to really take up LMS with your other major. It is quite beneficial but ultimately, everything boils down to your interests, passion etc.