To examine the relative performance in number sense among low-SES students, new immigrant students, and typical learners in grades 4 through 6, data were collected through a number sense web-based, two-tier test. A total of 628 fourth graders, 535 fifth graders, and 524 sixth graders in Taiwan participated in this study. Results showed that there were statistically significant differences in number sense performance among new immigrant children, low-SES students, and typical learners in the fourth, fifth, and sixth grades. The subsequent post hoc comparisons indicated that there was a statistically significant difference between typical learners and new immigrant children in fourth and fifth grades. Moreover, there were statistically significant differences between typical learners and low-SES students in fifth and sixth grades. The Chi-squared test results also showed that there were significant differences in the uses of solution methods between the fourth, fifth, and sixth graders. Implications of this study and suggestions for the future studies are discussed.