To protect children and their personal information, FERPA and COPPA limit what data online websites can collect.
FERPA
Family Educational Rights and Privacy Act
"The Family Educational Rights and Privacy Act (FERPA) (20 U.S.C. § 1232g; 34 CFR Part 99) is a Federal law that protects the privacy of student education records."
COPPA
Children's Online Privacy Protection Rule
"COPPA imposes certain requirements on operators of websites or online services directed to children under 13 years of age, and on operators of other websites or online services that have actual knowledge that they are collecting personal information online from a child under 13 years of age."