I would have to agree with this. I would have struck a deal with him, try it for a month and if it doesn’t help we will stop, or something like that. This is going to come back and bite you in the butt when he finds out, but have a hunch you knew that when you decided to take this course. But, you did what you felt you needed to do and I know of some kids that honestly, sneaking it in would be better than letting them struggle without if it was the only choice. I would start thinking about how to tell him before he finds out another way and you have to back-pedal and try to save face.