Shear clumsiness?

I have a conundrum. For the last two months, I have been learning to cut hair using specific shears. They are lightweight, sharp, and I quickly learned to handle them with no mishaps. Now that I am working on real people, I am told to use different shears that were included in my kit. They are bulkier, heavier, and a good ¼" longer than the others. Because of this, every time I have used them on a real person, I've cut myself. The first time was the tip of my thumb while I was cutting my brother's hair. Luckily, it was shallow and healed relatively quickly. The second was the cut in my previous post, which after nearly a week, has finally developed a scab, but still hurts like the dickens. The 3rd and 4th I acquired while cutting my mom's hair Thursday. They are both on my left index finger, both shallow, but both uncomfortable. The answer seems to be that I need to go back to using the original shears. The reason this is a conundrum at all is because my school considers the other shears to be "mannequin shears" even though they are reasonably expensive ($90) and made for people. They just won't let me use them. I think I'm going to have to show them my marred left hand as substantiation that the $200 shears are a hazard and ask for a refund.