Somebody help me understand this about trading schools

Few of my friends have paid some good amounts for trading schools. and another colleague pays for this whatsapp group where they share stock tips. When asked, all of them told that these expert traders are making this much profit. But when asked more, turns out its just their word? Their stock positions are not open and transparent at all? So there is no way to verify the trades? I am completely confused on how they are even making money and how they are getting people to pay. Does anyone know any expert traders who have their positions public?