According to the Simple View of Reading, decoding and linguistic comprehension are essential for reaching efficient reading comprehension. Students with Swedish as a first (L1) or second language (L2) in grades 1-3 might need special support to develop reading comprehension. In order to identify needs in reading in L1 and L2 students, the current study aimed to investigate how they perform in screening tests measuring vocabulary, decoding, and reading comprehension in Swedish. The present study has a cross-sectional design and includes over 46,000 students who followed the curriculum for Swedish as a first or as a second language. Data consisted of decoding, vocabulary, and reading comprehension tests, which were statistically analysed. The results showed that L2 students in grades 1-3 had significantly weaker decoding, vocabulary, and reading comprehension than L1 students. A performance below average in the tests indicates a need for extra support in reading which a significantly higher proportion of L2 students had compared to L1 students. Therefore, screening and systematic reading instructions are crucial to promoting reading development among L1 and L2 students.