Learn Hardcore Indonesian: Petugas menjaga kebersihan kelas setiap pagi. - The staff maintains the classroom’s cleanliness every morning.

petugas kebersihan (cleaning staff/janitor), or
petugas piket (students on duty for classroom chores). Without context, petugas is generic “the person/people responsible.”

Is petugas singular or plural in this sentence?

Indonesian doesn’t mark number on nouns, so petugas can be “attendant” or “attendants.” To make it explicit:

singular: seorang petugas (“one staff member”)
plural (people): para petugas (“the staff members”), or beberapa petugas (“several staff members”)
with numerals you usually add the classifier orang: dua orang petugas (“two staff members”)

Why say menjaga kebersihan instead of membersihkan?

menjaga kebersihan = “maintain/keep up cleanliness” (ongoing standard; includes ensuring it stays clean)
membersihkan = “to clean (something)” (the act of cleaning) So your sentence emphasizes maintaining cleanliness every morning. If you want the act of cleaning, say: Petugas membersihkan kelas setiap pagi.

Why use kebersihan (a noun) rather than bersih (an adjective)?

Bersih = “clean” (adjective).
Kebersihan = “cleanliness” (noun) formed with the ke- -an pattern. It turns qualities into abstract nouns, e.g. adil → keadilan (justice), benar → kebenaran (truth). After menjaga, a noun fits naturally: “maintain cleanliness.”

How does kebersihan kelas mean “the cleanliness of the classroom”? Why not say kebersihan dari kelas?

Indonesian commonly expresses “of” by placing nouns together: head first, modifier second.

kebersihan kelas = “cleanliness (of) classroom”
Using dari (“from/of”) is usually unnecessary here; kebersihan dari kelas sounds unnatural or overly literal.

Can I say “keep the class clean” as menjaga kelas bersih?

Not idiomatic. Use:

menjaga kebersihan kelas, or
menjaga agar kelas tetap bersih (“keep the class so that it stays clean”) Directly attaching an adjective after the object with menjaga doesn’t work the way English “keep X adj” does.

Does kelas mean the room or the group of students here?

Here it most likely means the physical room (“classroom”). Context decides. If you need to be explicit, say ruang kelas for the room, or refer to a class group like kelas 3A.

Where can I put setiap pagi in the sentence?

Neutral positions:

End: Petugas menjaga kebersihan kelas setiap pagi.
Front (with a comma): Setiap pagi, petugas menjaga kebersihan kelas. Both are natural. You can also use the shorter synonym tiap pagi.

Is di setiap pagi correct?

Avoid it. Say setiap pagi.
If you mean a general time-of-day (not “every”), you can use:

pada pagi hari (more formal) or di pagi hari (common in speech) = “in the morning.”

How do I talk about past or future time with this sentence?

Indonesian has no tense on the verb. Add time words or aspect markers:

Past: tadi pagi, kemarin, or aspect sudah/telah
Example: Tadi pagi petugas menjaga kebersihan kelas.
Progressive: sedang
Example: Petugas sedang menjaga kebersihan kelas.
Future: besok pagi, nanti pagi, or akan
Example: Besok pagi petugas akan menjaga kebersihan kelas.

How do I negate this sentence correctly?

Use tidak before the verb:
Petugas tidak menjaga kebersihan kelas setiap pagi.
Use bukan to negate nouns/adjectives, not verbs.

How would I say this in passive voice?

Use the di- passive:

Kebersihan kelas dijaga (oleh) petugas setiap pagi. The agent oleh petugas is optional; you can drop it if it’s obvious.

How do I specifically say “the cleaning staff clean the classroom every morning”?

Use the more specific subject and the “clean” verb:
(Para) petugas kebersihan membersihkan kelas setiap pagi.

What does the prefix in menjaga do?

The base is jaga (“guard, look after”). The active transitive meN- prefix makes menjaga (“to guard/maintain”). With roots starting with j, meN- surfaces as men- → menjaga.

Are there good synonyms or near-synonyms here?

menjaga kebersihan (most common collocation)
memelihara kebersihan (maintain cleanliness; a bit more formal)
For tidying: merapikan kelas (“to tidy the classroom”) Choose based on the nuance you want: maintain vs clean vs tidy.