Is the challenge of science literacy based on a misguided focus in teaching?

Nordic learners’ performance in the reading and science literacy of PISA by OECD has declined considerably over the last decade. The defined PISA proficiency is in line with the aims of our curricula. Then, why is reading and science proficiency getting worse? How and where can we advance to improve the situation? Extensive international research indicates that to grasp the central meaning of a text an understanding of 98% of the words is required (Hu & Nation, 2000; Laufer & Ravenhorst-Kalovski, 2010; Schmitt et al., 2011). Vocabulary plays thus a pivotal role in reading comprehension. The number of words in each language is countless, and therefore it is useful to divide vocabulary roughly into high- and low frequency words. Drawing from research on reading and science literacy I will ask if science teachers need to change their focus in teaching, taking systematic notice of word frequency in their language. The high frequency words fall into Tier 1, whereas the low-frequency words either belong to Tier 2 or Tier 3. Words in Tier 3 are specialised vocabulary, concepts that have defined meaning within each subject field, e.g. carbon, and multiplication. These words are specially taught by teachers and explained in textbooks (Beck et al., 2013; Roessingh, 2016; Snow, 2016). Words in Tier 2 are however used across diverse disciplines, are more common in academic writing than in oral language but do rarely get the attention in teaching (Calderón o.fl., 2005; Roessingh, 2016; Sigríður Ólafsdóttir et al., 2020). These words do not have a key function in academic texts, but these words support what is explained or discussed. Thus, words in Tier 2 are ‘the tools’ we use to explain words in Tier 3.