We examined the efficacy of two interventions aiming to strengthen argumentative text comprehension in Greek secondary students with specific reading disability or low reading achievement of unspecified cause. The first intervention (control group, n = 29) was based on principles of systematic explicit instruction, whereas in the second one (experimental group, n = 30) the repeated reading strategy (RRS) was added. Both the control and the experimental groups included students with specific reading disability or low reading achievement. The control group received 24 lessons of 60 min each, whereas the experimental group received one extra lesson to ensure participants' familiarisation with the use of RRS. Both groups presented significantly higher achievement at post-test than at pre-test, as shown by measurements for which a standardised and a researcher-made reading comprehension tool were used. The effect size of both interventions was high (control group: 0.85, experimental group: 0.81). Results are discussed in terms of the effectiveness of systematic explicit instruction in teaching argumentative text comprehension to secondary struggling readers.