Last minute productivity

Teachers always used to tell me I can't study one day before the exam or I can't start an assignment 1 week before the deadline, but I often do and did these and it always worked out well for me. Why fix something when it isn't broken? Best part is, after doing all of this, I mostly still ended up receiving one the highest grades at the same teacher that told me not to do it. My last minute productivity has saved me countless times and I feel like it will continue to do so. There's probably a scientific reason behind it, but I never looked into it. Maybe I will one day though, just not today or anytime soon.