Learn Hardcore Indonesian: Guru menempel jadwal ujian di papan tulis dengan lem agar semua murid melihatnya. - The teacher sticks the exam schedule on the board with glue so all students can see it.

To make it clearly “a/one,” use seorang: Seorang guru menempel…
To make it clearly “the/that,” use itu: Guru itu menempel…, jadwal ujian itu

What does menempel mean, and how is it formed from tempel? What’s the difference between menempel and menempelkan?

Base verb: tempel “stick/attach.”
Active form with meN-: menempel. The initial t drops and the prefix becomes men- (meN- assimilation): tempel → men- + (t)empel → menempel.
menempel can mean “to stick/adhere,” intransitively or (in everyday speech) transitively:
- Stiker itu menempel di dinding. “The sticker is sticking on the wall.”
- Guru menempel jadwal… (colloquial transitive)
menempelkan is the explicit transitive “to stick (something) onto (something)”:
- Guru menempelkan jadwal ujian pada/di papan tulis.
  It’s more “by-the-book,” and often preferred in formal writing when two participants (object and surface) are mentioned.

Is menempel jadwal ujian di papan tulis actually correct, or should it be menempelkan … pada papan tulis?

Both are widely used and acceptable. In formal style, many prefer the more explicit menempelkan [obj] pada/di [surface]. In everyday Indonesian, menempel [obj] di [surface] is very common and natural.

Why di papan tulis and not ke or pada?

di marks location (final place): “on the board.”
ke marks movement/direction: “to/onto the board.” Works well with menempelkan when you stress the motion: menempelkan … ke papan tulis.
pada is a more formal/neutral “on/at/to” for targets: menempelkan … pada papan tulis.
Your sentence focuses on location, so di is perfect.

What exactly does papan tulis refer to?

Literally “writing board.” It’s a generic term for classroom boards—blackboard or whiteboard. If you need to be specific, say papan tulis putih (whiteboard) or papan tulis hitam (blackboard), though that’s rare in casual use.

What does dengan lem mean? Can I say pakai lem or menggunakan lem instead?

All mean “with glue”:

dengan lem = with glue (neutral)
pakai lem = use glue (colloquial)
memakai/menggunakan lem = use glue (neutral/formal) All are fine here.

What does agar mean, and how is it different from supaya, biar, and untuk?

agar and supaya: “so that/in order that” + full clause. agar is a bit more formal; supaya is neutral.
- … agar/supaya semua murid (bisa) melihatnya.
biar: informal equivalent of supaya.
untuk: “for/to” but not used before a finite clause. It takes a noun/verb phrase, not a full S+V clause:
- Natural: … agar/supaya semua murid bisa melihatnya.
- Not natural: … untuk semua murid melihatnya (as a finite clause).

Why is it melihatnya? What does the suffix -nya refer to? Could I say melihat itu or drop it?

-nya here is a third-person singular object pronoun “it/him/her,” attached to the verb: melihatnya = “see it.” It refers to jadwal ujian.
Alternatives:
- … melihatnya. (concise, natural)
- … melihat jadwal itu. (explicit)
Don’t drop the object entirely; … agar semua murid melihat is incomplete here because it doesn’t say what they see.

Why use melihat instead of the base lihat?

melihat is the active verb with the meN- prefix, standard in statements. The bare root lihat appears in imperatives or very casual speech:

Saya melihat jadwal itu. (standard)
Lihat! “Look!” (imperative)
Very casual: Supaya semua murid lihat (you’ll hear it, but it’s informal).

Can I change the order of di papan tulis and dengan lem?

Yes. Indonesian is flexible with adverbials. Both are natural:

… menempel … dengan lem di papan tulis. (Manner → Place; many style guides prefer this order)
… menempel … di papan tulis dengan lem. (Place → Manner; also common) Choose what sounds smooth in context.

Is semua murid the only way to say “all the students”? What about para murid, murid-murid, or seluruh murid?

semua murid = all students (very common)
para murid = the students (plural, people-only, slightly formal/literary)
murid-murid = students (plural via reduplication)
seluruh murid = the entire body of students (emphasizes totality) Don’t combine semua/para/seluruh with reduplication: say semua murid, not semua murid-murid.

Does -nya mean singular only? How would I say “so that all the students see them”?

Yes, -nya is singular. For plural objects, use an independent pronoun:

… agar semua murid melihat mereka. (“see them”) You can also name the plural noun explicitly:
… agar semua murid melihat pengumuman-pengumuman itu.

Do I need to add bisa/dapat after agar?

Not required, but adding it can make the idea of ability/possibility explicit:

Without: … agar semua murid melihatnya. (so that they see it)
With: … agar semua murid bisa/dapat melihatnya. (so that they can see it) Both are correct; the version with bisa/dapat is slightly clearer.

Is there any nuance between murid, siswa, and mahasiswa?

murid and siswa: school students (elementary–high school). siswa is a bit more formal/administrative.
mahasiswa: university/college students. In your sentence, murid is the default and perfectly natural.

Is jadwal ujian a compound? Why is the order “schedule exam” and not “exam schedule”?

Yes. Indonesian puts the head noun first, then the modifier:

jadwal (head) + ujian (modifier) = “exam schedule.” This head–modifier order is the norm for noun–noun compounds in Indonesian.