This is an interesting study nicely summarized in The Bulletproof Musician.

Learners exposed to two different study methods - blocked vs interleaved practice - preferred the blocked practice method, a learning method known to be less effective. Rather than attribute it to laziness, the authors of the study hypothesized that learner’s simply don’t know what method of practice (study) is more effective so that interpret the more difficult method (interleaved) as being harder.

For me, the takeaway here is that we have to train ourselves and kids to be mindful of the connection between effort and effectiveness.