First of all ... Don't get all worried about that stuff you are hearing -- and don't think it will all apply to the program you choose. Each nursing program is different -- with different requirements, procedures, etc. This discussion site includes people from all over the world and from all different types of educational programs. So, what you are reading is a hodge-podge comination of everything out there.
As you go through the process of selecting a program, interviewing, etc. you will learn more about the particular programs you are considering. For example, some require that you take certain courses as prerequisites (such as anatomy and physiology, psychology, English, etc.) and THEN apply to enter the nursing program. Others accept students right out of high school and then include those courses as part of their program.
One aspect of most nursing schools generates a lot of anxiety among students is the need for the profession to assure that its members can achieve a near-perfect performance in patient care while under pressure. For example, if a nurse is only giving 80% of her medications correctly, she is probably hurting a lot of his/her patients. Similarly, if a nurse fails to maintain asceptic technique while performing clean/sterile procedures, the patient can suffer serious harm. And nurses must be able to think clearly and perform well under pressure in real-life situations. Therefore, most nursing schools have various skills check-offs and tests built into the curriculum that students must pass with very high scores. Typically, they give the students 2 or 3 tries to pass the test, but there is usually some cut-off point at which the student has to face the "if you can't perform at this level by the end of this time or after the set number of tries," they fail the course.
Similarly, nursing schools may have stricter rules about attendance and/or handing homework in on time, etc. that other academic disciplines insist upon. Again, this is because, even as students, future nurses are entrusted with the well-being of others. You can't take care of a patient properly if you haven't done the necessary homework. So, that values of always being prepared, fulfilling your committments to hand in your work on time, etc. are more emphasized in nursing programs than most other courses of study.
Having to live up to these professional standards of performance and behavior is often stressful for students -- particularly for those who may be accustomed to an "80% is good enough" environment often found in other fields, high school, etc. It may also be the first time that student are graded, not just on how well they could recall information, but on how well they used information to make a decision,how well they performed a technical procedure, and/or how they interacted with someone.
As some of their classmates fail to live up to the high expectations, it becomes even more stressful. They feel compassion for their "fallen" classmates and worry about whether or not they can meet the requirements. And also, there is the ocassional "mean" teacher or set of requirements with which the students disagree.
This forum is one place where students can vent those anxieties, compare notes with students in other programs, and find emotional support and some practical advice for dealing with the stress of being a student. That's a good thing. ... but someone like you needs to understand that you are sometimes listening in on a "gripe session" that may not refect the reality of the situation that you will face in your your real life experiences.
You need to learn to put it all in perspective. At the college level, some of your classmates will not pass a given course and move on to the next level. Most students don't have that experience in high school. Your friends may fail a test, get a "D" in a course, etc., but they continue on and pass to the next grade. In nursing school, if you fail certain tests, etc. you don't move on to the next level with a bad grade. You're out: or at least have to repeat the course.
Good luck with your admission to nursing school. It can be a wonderful profession and you can have a great career and life as a nurse. Just don't expect it to always be easy.