French instraments, do i use du, de la, or des?

It depends on the instrument and whether you mean to say "playing a guitar" for example, or just "a guitar".

1. la rentrée is the first day back to school in the fall.
false (la rentrée is the first day back to school in summer)
la rentrée est le 3 septembre c'est encore l'été, l'automne est le 22 septembre)

2. in france, students take an exam at the end of their high school education. if they pass it, they can go to the university.
true

3. le bac is the test that is taken every year at the end of the year.
false
(en fin de terminale, les lycéens passent le baccalauréat)

4. french teenagers do not generally get part-time jobs because their homework keeps them plenty busy.
false

5 teenagers cannot drive in france until they are 18-years-old.
true
(conduite accompagnée : 15 ans)

6. the homes in france are generally made of different materials than most homes in the united states.
true

Already answered but thanks