Community colleges across the United States are increasingly linguistically diverse, with populations that often include immigrant students who have grown up with a language other than English but have spent a significant part of their childhood in the U.S. and as such received a substantial part of their -K-12 education there. In this paper, we analyze perceived second language (L2) effects in essays written by multilingual "resident," i.e., immigrant, students enrolled in pre-credit bearing developmental and ESL writing courses. Focusing on a predominant set of grammatical patterns identified in previous research, this study compares the writings of L2 resident students to those of monolingual and international L2 students. Findings reveal that the age of arrival to the U.S. impacts grammatical patterns, with L2 resident students arriving after age 12 displaying residual grammatical L2 acquisition effects, as contrasted with earlier arrivals, whose writings resemble monolingual students' more closely. As familiarity with "standard" English patterns is unfortunately often viewed by community college instructors as indicative of "academic" writing ability, we argue that these findings indicate a need for community colleges to consider students' linguistic histories and their effects in order to interpret resident L2 students' writing skills correctly and to provide appropriate linguistic support for resident L2 students across the curriculum. Professional development that emphasizes critical language awareness is needed so that instructors can better understand and support linguistic diversity in their classrooms.