During use of touch-screen tablet devices, the user's hand can occlude regions of the screen. Here, we present results from an exploratory study of hand orientation and occlusion among American primary school students using a touch-screen tablet device. We investigated hand orientations, amount of occlusion, and the effects of tablet tilt angle (flat or tilted) on students preferred hand orientations when using a touch-screen tablet device. From 18 interviews with 5th-7th grade students using interactive science simulations, we found five common hand orientations corresponding to a range from high to low occlusion. Tablet tilt angle considerably impacted students preferred hand orientations. Based on these results, we suggest that encouraging students to work on tablets with a moderate tilt angle (30-45 degrees), rather than lying flat on a table, could significantly decrease occlusion and increase the effectiveness of touchscreen tablet devices for learning.