As many students begin the new school year Tuesday, they’ll also bring home their first homework assignments of the new school year. Although it’s generally assumed that homework helps students learn, a review of the research reveals a surprising verdict: It’s complicated.

Matt Barnum at The 74 looked at what research says about homework’s effectiveness. “Shockingly little, as a matter of fact,” Barnum writes. It’s not that research says homework is ineffective or that there’s plenty of research with inconclusive results on homework’s effectiveness. There just isn’t much research at all and that research should be taken with more than a few grains of salt.