In the third year, they moved upstairs and continued to drag their trolley bag up and down the stairs because they preferred it that way. They didn't mind dragging the bags up and down the stairs as long as they could roll it when they were on the ground floor as it was a distance from the stairs to the school lobby. So, their bags went thump, thump, thump as they dragged it up and down the stairs. I don't know how they did it.
However, the books and workbooks kept on increasing and finally, they had to resort to carrying another hand carry bag, usually a recycle bag. Soon, that recycle bag was filled to the brim especially my girl's as she is one diligent kid who likes to have her books around her so she won't miss any homework. So, we got her a backpack and she ended up carrying a backpack AND a trolley bag. On days when she has activities like art, she would take out her recycle bag to put her art stuff. So she had her backpack, her trolley bag AND a recycle bag.
Recently we got them new backpacks and proper hand carry bags instead of the flimsy recycle bags. We didn't realize that the backpack was too big for my boy, so on the first day he carried it, it slipped off his shoulders and stayed strapped onto his waist! Fortunately, no one was hurt in the incident. He only had to put up with some laughter from other children and the teachers around him because he looked so strange carrying a backpack that was strapped to his waist.
Now both of my kids carry two bags to school and both bags are just as heavy. Trolley Bags or Backpack? Heck, they need both!