3. Employment Authorization and Attending School under TD Visa Status:

The spouse and/or child of a TN visa worker “shall not accept employment in the United States unless otherwise authorized.” 8 C.F.R. 214.6 (j) (3). If a TD dependent wants to work in the U.S., "he or she must independently seek change of status to an employment-authorized nonimmigrant classification.” 58 FR 69205, 69209 (Dec. 30, 1993).

However, spouses and children in TD visa status are permitted to study: “Dependents in TD status may attend school in the United States on a full-time basis, as such attendance is deemed to be incidental to their purpose for being in the United States, which is to accompany the TN alien.” 58 FR 69205, 69209 (Dec. 30, 1993); 9 FAM 41.59 N12.1; INS Manuals § 15.5. See also 67 FR 18062, 18062 (April 12, 2002).

Prospective students in TD status should be aware that many schools may consider them non-residents for tuition purposes and therefore subject them to higher tuition rates.

http://www.tnvisabulletin.com/spouses-and-children/