re: How to unlock lock screen password?

I plan on doing that when he gets home from school, but I was hoping to access it and change the password to one he doesn't know. I want to see how long it takes him to ask me about it. I took his tablet and phone away a couple of days ago. I gave his phone back in order to have to get in touch with me when I'm not home. Now he has locked it which tells me he's up to no good. Lol.