If the site is hosted in the United States, you should first send her a DMCA take down letter and maybe that will end it. When it comes to minors, and adults for that matter, when companies use photos of their customers for marketing they must have explicit permission. Otherwise they are exposed to liability. Because the photos are of minors, there are even more stringent controls over this. I would recommend sending a letter to the gym to take the photos down. First, though, make sure that when you signed up to the gym you did not consent to use of photos in any contract with the gym owners.
Demand letter first, then lawsuit if you are really committed to having them taken down. You will need to see a lawyer in Canada if the gym is located in Canada. Though Canada's laws governing this type of event are usually more specific and protective, especially of children.
The recommendations in this answer are not considered legal advice for the purposes of ethical, legal and practical evaluation, nor does this recommendation create a retention of counsel agreement between us, wherein an attorney-client relationship exists. These recommendations should never be relied upon without first consulting an attorney in your jurisdiction. I am not your attorney, unless we enter into a written agreement fulfilling the terms of that agreement. The comments posted herein are purely for educational purposes and public discourse only.
Not an appropriate use of the photo without permission. Send the demand letter, as my colleague suggests. That should work. If there is no action, contact an attorney. You could try the one last verbal attempt for the sensei. She may not be posting / maintaining her own site, and so encountered some delay. OR, you could leave the pictures up. My dojo did not ask me, but I didn't worry - it was just part of our collective kai, our "spirit."
We do not have a client/attorney relationship until you make an appointment, we discuss your case face to face, I accept a retainer, and we explictly agree to enter into representation.
Many businesses that offer an activity-based service require parents/participants to sign a photography release at the time they enroll. You should check the agreement that you have with the jiu jitsu studio to make sure you did not inadvertently give such consent for her to use your childrens' pictures. She may still take them down of her own free will, but if you gave your consent, you will not have legal action against her.
No Attorney-Client Relationship. This post has been prepared by Inna Efimchik of White Summers for general informational purposes only. The information provided herein does not constitute advertising, a solicitation or legal advice. Neither the availability, transmission, receipt nor use of any information included herein is intended to create, or constitutes formation of, an attorney-client relationship or any other special relationship or privilege. You should not rely upon this post for any purpose without seeking legal advice from licensed attorneys in the relevant state(s).