Exam system in high school

I came to japan after a long time to continue my studies in japan and i want to join shibata minami high school i know everything about entrance exams and i am preparing for it aswell but one question is irritating me and i cant find any answers online so i am asking here so is there exams in high school like there are 3 years of high school right? so in a single year how many exams will held when i finish my first year is there any exam? like of i didn't pass it i cant go to my second year? i read somewhere that it depends on points i dont get it what is points in high school it says if you didn't reach the goal you wont pass the year so please help me out

Per school term there will be one mid-term test and a final test. Some schools have 3 terms to one school year, some others might have 2. And that is per subject (like English, Japanese grammar, world history, Japanese history, math, biology, etc.).

Usually they have a threshold like 30 points out of 100 full score, below which is gF,h failing that test, after which you might have to sit for additional class hours and/or re-sit the test.

Whatever question you have about senior high school can be answered through the particular school's official website or by sending an inquiry to the school itself. For public schools, the board of education can often answer your questions.

From Shibata Minami High's official website, click ”NŠÔsŽ–—\’è and you can see exam dates among other dates for the year.
http://www.shibatami-h.nein.ed.jp/
http://www.shibatami-h.nein.ed.jp/pdf/h31nenkan.pdf
Whatever question you have about senior high school can be answered through the particular school's official website or by sending an inquiry to the school itself. For public schools, the board of education can often answer your questions.

Whether you flunk a year or you simply have to drop out of the school itself depends on the specific high school. I'm not sure what is the case for Shibata Minami. Unlike junior high school, senior high school is not compulsory education in Japan, so it's easier to drop out from than junior high. But the pressure also helps you to keep trying.

Generally speaking, if you are qualified enough to pass the entrance exam, you can usually graduate as long as you are a serious student. In other words, the entrance exam is usually the hardest part, unless you stop trying after you enter the school. Needless to say, there are also pop quizzes and homework, which also, along with your attitude, influence your grades.

As for "points", I think you mean "tan-i" which is also translated as "credit" or "unit". Like any school around the world, you need to gain a certain amount of them in order to graduate. Most (but not all) high schools in Japan take care of your curriculum so that you will automatically gain designated "tan-i" as soon as you finish seriously studying the subject for each year.

In any case, studying is always worth while, even if you don't reach your immediate goal. Keep working!