The main aim of this study was to investigate theeffect of a tier three intervention, response-tointerventiondesign, on children with low readingability in grade three. Twenty-eight children (12females and 16 males) participated in this study.The participants were given out a battery of readingtests including decoding and reading comprehensiontests, and in total, the children received20 reading intervention sessions in two waves, during4 weeks. The results showed substantial gainswith large effect sizes (d 0.78–2.95) on all thereading tests after the intervention period. A short,intensive and individualised intervention has a substantiallypositive effect on children’s reading ability.For a majority of the children, the increasedability sustains even 4 years after the end of theinterventions. However, as boys seem to have thegreatest problem to sustain their increased ability,the authors claim that it is important to continuethe intervention even after the research interventionshave ended.