For Mac OS users, there is a system setting that may not allow you to tab onto several types of elements in a web page. To change this setting:
ELAR: 8:15-10:15
Math: 10:15-11:35
Lunch/Recess: 11:45-12:30
Specials: 12:45-1:30
RTI: 1:45-2:30
Science/Social Studies: 2:30-3:15