The single most useful safety measure for an online class is that a parent can see and hear it. Unlike a classroom across town, an online lesson happens in your own home, a few feet away from you. Nothing has to be taken on trust: you can watch the whole thing, every time, if you want to.
Many parents sit beside their child for the first few classes, then listen from across the room once they know the teacher. With younger children we recommend staying close throughout. There is no point at which you lose the right to sit in.
Keeping the same teacher each week helps here too. You hear how they speak to your child, how they correct mistakes and how they handle a tired or distracted day. Over a few weeks you build a clear picture of the person teaching your child, which is far more reassuring than any badge on a website.