VASCHYMen's Backpack, Women's Waterproof School Bag, Boy Girl Computer 15.6 Inch Vintage for School, College, Work, Travel, Leisure

Q: does an a4 folder fits?

I don't know for sure. It was for my grandson but I believe it will.

Q: Is this backpack good for highschool? My kids have to carry large binders/chrome book/supplies. Is there enough room for all of that?

Honestly, if they have to carry more than 3-4 large books & supplies, I would opt for a larger size. The sides of this backpack don't expand that well. I carry a pair of sneakers, my lunch, and this laptop in the pack comfortably. But that's about it. Although the way this pack handles weight is amazing! No back stress at all! Hope this helps.