It’s a sign that your wife is a cheating liberal feminist sl*ut.
The problem isn’t you... it might not even be your marriage. The problem is that she’s become indoctrinated into the leftist Democrat school culture that brainwashes women to hate men, (especially white men), and to not have any pics with them or to show that they love or respect them. This culture encourages cheating on white men.
Your wife is just doing what she thinks she needs to do to be accepted, respected and loved at school.
If I were you I would definitely talk about it though. I would ask her point-blank why she is doing this to you and your marriage. Make it clear that what she’s doing is shameful, wrong, and it’s a public attack on y’alls marriage. And tell her if she wants to stay married, you expect her to keep a pic of y’all kissing or some sweet pic of you two clearly being a couple, showing visibly on her desk at school at all times.
Sometimes you have to just lay down the law and stop being a cuck
Your wife obviously thinks that it benefits her to not have a picture of you two together. Either because she’s cheating, or because she’s a liberal cuck who thinks it’s “cool” to be independent and disrespect her husband, or both.
What you need to do is make her realize that it’s going to be much more painful, harmful, and inconvenient for her to NOT put y’alls picture up.