Both DS and DD took the Explore last year as 3rd graders. They were both fine. The actual test is only two hours (1/2 hour each for 4 sections), but you have to add time waiting for everyone, filling out the personal info, doing the few practice questions and a break in the middle. DS finished with a lot of left over time in each section, while DD didn't have enough time to finish any of the sections. It wasn't that stressful for either of them, but they do not have anxiety issues in general.