Dual language programs are poised to produce bilingual/biliterate teacher candidates to alleviate bilingual educator shortages. Therefore, in search for ways to support the growing number of Spanish/English dual language programs in Texas, the authors of this paper analyzed the variations of Spanish language and proficiency levels of 9th grade heritage Spanish speakers. Researchers analyzed 62 students' written and oral productions in Spanish through an error analysis approach. The results obtained from this analysis were crossed-checked with academic and personal data, providing important information on the linguistic needs as well as the factors mediating the different levels of Spanish proficiency demonstrated by the students. Furthermore, a differentiated instructional methodology was established to bridge students' specific needs with effective practices. Written academic language was planned with the group of native-like speakers, whereas speaking activity centers were implemented for the group of students with a passive use of Spanish, and game-like experiences for those heritage speakers who had lost much of their Spanish abilities. The findings from the study illustrate that by understanding Spanish heritage speakers' unique abilities and needs, instruction can be created that will build their ability and confidence with their language.