A growing number of studies have probed the effectiveness of certain exercise formats in the learning of multi-word expressions (MWEs) in classroom settings. However, a number of important variables, such as MWE retention over an extended period of time and the role of repetition, have so far not been considered. Furthermore, studies have focused primarily on university level learners, with young L2 learners being almost entirely disregarded. The present study sought to address these gaps with 148 high school students who were randomly assigned one of three fill-in-the-gap exercises: (1) word-format, where participants selected the appropriate verb from a list provided; (2) letter-format, where the first-letter of the missing verb was provided as a clue; and (3) phrase-format, where participants chose an appropriate intact phrase from a list. Participants did the exercise once, twice or three times. The study investigated the effects of exercise format and repetition on the learning of 20 verb-noun collocations, one and eight weeks following the treatment. Results from generalized linear mixed-effects modeling showed that both exercise and repetition had significant impact on the learnability of the target MWEs, but the format had a smaller effect size than repetition. Rasch analysis was also used to examine the potential difference in the difficulty of MWEs, and how this difficulty may interact with the exercise format. The findings largely support previous research, but also underline the importance of repetition and suggest that exercise format does not uniformly interact with the learnability of MWEs.