ye thats the case for Australia,
every other year means absolutely nothing towards our ATARSCORE (our final mark after year 12, highest atar is 99.95) unless you have done a year 12 or university subject in those years,
when we do our mid year and end of year exams,
we are scaled against the rest of the country so there could be only a couple of marks on an exam which switches your grade from a D+ to a B,
and since exams count for 50 or 66.66% of our grades, they are pretty important.
hope this helps turbo, and if you ask your teachers about it, they can explain it all to you
edit: btw, English is the most important subject that counts towards your ATAR since every person undertaking Year 12 has to do an English subject (im not sure about other states but this is the case for Victoria)