It is going to be variable based on a number of various factors.
Different states have different requirements, and depending on the School/School District, Community Size and general "wealth" of both the Scool District and the school's patrons(parents) also factor in.
Which isn't to mention format variations. Rural Districts can have "secondary" start in either 6th or 7th Grade, where they are in turn attending either a "Middle School"(highest grade is 8th), a "Junior High"(Highest grade can be 9th grade--High School Freshmen in most of the country. Yes, that means officially starting "Senior High School" as a Sophomore), or some flavor of combined Middle/Junior/Senior High School.
Which likewise means you could have either a 3 year, or 4 year high school format depending on the Middle School/Junior High aspect. Middle schools can likewise be two, or three year institutions.
I graduated HS in 1998(So I guess I'm a prime interview target in that respect, having actually been in High School in 1995). My experience was a 3 year Junior High and 3 year senior high. After they built a new additional High School, the graduating class of 2007 in that same district attended a 2 year (grades 7 and 8) Middle School, followed by 4 years of High School. The graduating class of 2018, in the same district, will have attended a 3 year Middle School(grades 6 to 8), and a 4 year High School.
In the case of that school district, as with most of them, a lot of that was a function of capacity. The 3rd High School opened up enough space to pull the 9th graders in, and with the easing of a "student population bubble" they shut down one of Junior Highs(one less Administrative staff to pay for) and shuffled the remaining students from that school out to the other rebranded Middle Schools that just lost a 3rd of their student body. Not quite a decade later, crowding in the Grade Schools became sufficient that they reopened the closed Junior High as a Middle School and incorporated 6th graders into all of the Middle Schools in order to create room in the Grade Schools. But that's a digression.(But potential background fodder for how/why your particular School is setup as it is)
Larger(population)/better funded districts will, obviously, have more options for their students. Larger student bodies usually mean more options, but not reliably so, as people in an "Inner City" type school might attest.
People attending high school in a College/University Town/City are likewise going to have better options as interactions with the local College/University is very likely to result in AP(Advanced Placement) programs being available where some High School classes could earn college credits.
Proximity of High Schools to each other can also come into play. There were programs that were unique to each High School in my district and a busing program to shuttle students between schools(during lunch) existed for people enrolled in those more unique offerings for example.
At the time I attended, the Junior High ran on a 7 (class) period schedule that was the same every day. The High School ran on a 6 (class) period schedule, that likewise was the same every day. Lunch wasn't considered one of those periods, although a first/second lunch did exist on the schedule.
There were courses that had options for being taken as a scheduled class in the hour before, or the hour immediately after the normal 6 period schedule. Night school classes (typically remedial) were offered as well, but you paid extra for those, and those were more in line with the "college format" of MWF or Tu/Th.
Summer School also was available as an option for those needing either remedial education, or for those trying to knock out general requirements for graduation to either pursue additional electives during the school year or pursuit of early graduation. Generally speaking there were few "hard" restrictions in regards to what had to be taken when, so long as the pre-requisite course requirements had been met(or the instructor accepted the student by other means). You might need to speak to a guidance counselor to satisfy them that you have a "satisfactory" plan and the means to carry it out, but at least for my school, that was usually as far as things needed to go.
(For example on this front, I had electives I wanted to take and the 6 period schedule wasn't sufficient to cover all the General Requirements for graduation and do those electives. So I enrolled in Summer School, and took care of my mandatory 2 semesters worth of Phys Ed over the summer, so it never was part of my High School school day)