Learn Hardcore Indonesian: Saya menaruh buku ke dalam tas sekolah saya.

If you remove the final saya, you just get tas sekolah = a school bag (not specifically my school bag).
If the context is already clear, Indonesian speakers might drop one of them in casual speech, but grammatically both roles (subject and possessor) are separate.

What exactly does tas sekolah saya mean? Is it “my school bag” or “the bag of my school”?

Normally tas sekolah saya is understood as “my school bag”:

tas = bag
sekolah = school
tas sekolah = a bag used for school / school bag
tas sekolah saya = my school bag

Technically, it could also be interpreted as “the school bag of mine” or “the bag of my school” depending on context, but in real life, when someone says tas sekolah saya, people will almost always understand my school bag (the bag I use to go to school).

To clearly mean a bag that belongs to my school (the institution), you would usually add something like milik (belonging to):

tas milik sekolah saya = a bag owned by my school.

What’s the difference between saya and aku, and could I say Aku menaruh buku ke dalam tas sekolahku?

saya = neutral / polite, used in most formal and semi-formal situations.
aku = informal / intimate, used with friends, family, people your age, etc.

For possession, you can use:

tas sekolah saya = my school bag (neutral/polite)
tas sekolahku = my school bag (informal; -ku is a clitic form of aku)

So this sentence is perfectly natural in informal speech:

Aku naruh buku ke dalam tas sekolahku.

More formal and closer to your original:

Aku menaruh buku ke dalam tas sekolahku.

Just avoid mixing very formal and very informal forms in the same sentence in careful speech (e.g. saya with -ku).

There is no word for “a” or “the” here. How do articles work in Indonesian?

Indonesian doesn’t have articles like a/an or the. buku can mean:

a book
the book
books (in general, if context suggests plural)

You clarify if needed:

sebuah buku = a (single) book
beberapa buku = some books
dua buku = two books
buku itu = that book / the book (specific, known to both speaker and listener)

Does buku mean “book” or “books” here? How do you show plural?

By itself, buku is number-neutral. It can be book or books depending on context.

To show plural more explicitly, you can use:

buku-buku (reduplication) = books (plural)
beberapa buku = several books
banyak buku = many books
tiga buku = three books

So your sentence could mean:

I put a book into my school bag.
or
I put books into my school bag.

Context decides.

Why is the verb menaruh and not just taruh? When do I use the me- prefix?

taruh is the base form “to put/place”.
menaruh is the active verb form with the meN- prefix (here realized as me-):

Base: taruh
Active: menaruh

In standard Indonesian sentences, for active verbs you normally use the meN- form:

Saya menaruh buku… = I put the book…
Dia membaca buku. = He/She reads a book.
Mereka menulis surat. = They write a letter.

You use the base form (without meN-) mainly in:

imperatives: Taruh bukunya di sini! = Put the book here!
dictionary entries, word lists, etc.
casual speech, where people often say naruh (colloquial) instead of menaruh.

So in careful, neutral writing/speech, menaruh is the better choice here.

What is the difference between ke, di, and ke dalam? Why do we say ke dalam tas, not just ke tas or di tas?

Basic meanings:

ke = to (shows direction / destination)
di = at / in / on (shows location)
dalam = inside
ke dalam = into (movement into the inside of something)

In your sentence, you’re expressing movement into the bag, so:

ke dalam tas = into the bag

Comparisons:

Saya menaruh buku ke dalam tas.
I put the book into the bag. (emphasis on entering the inside)
Saya menaruh buku di dalam tas.
I put the book in the bag. (focus on its final location inside)
Saya menaruh buku di tas.
More like “I put the book on/at the bag” (e.g. on top of it), not inside.

ke tas by itself is unusual for this meaning; native speakers would say ke dalam tas when the idea is “into the bag.”

Could I say Saya menaruh buku di dalam tas sekolah saya instead? Is there any difference from ke dalam?

Yes, both are grammatical:

Saya menaruh buku ke dalam tas sekolah saya.
= I put the book into my school bag. (movement into)
Saya menaruh buku di dalam tas sekolah saya.
= I put the book in my school bag. (final location inside)

With a verb of placing like menaruh, native speakers often use either ke dalam or di dalam, and the difference is subtle.
In everyday speech, both will usually be understood the same way; ke dalam slightly emphasizes the motion into the bag.

Is the word order in Saya menaruh buku ke dalam tas sekolah saya fixed, or can I move things around?

The basic, neutral order is Subject–Verb–Object–(Place):

Saya (S) menaruh (V) buku (O) ke dalam tas sekolah saya (place).

You can move elements for emphasis or style:

Buku saya taruh ke dalam tas sekolah saya.
Emphasis on buku (the book(s)).
Ke dalam tas sekolah saya, saya menaruh buku.
Fronts the place phrase for emphasis; sounds more formal or literary.

For learners, it’s best to stick to the basic SVO order:
Saya menaruh buku ke dalam tas sekolah saya.

Can I omit saya at the beginning and just say Menaruh buku ke dalam tas sekolah saya?

You can drop the subject pronoun in Indonesian if it’s clear from context:

(Saya) menaruh buku ke dalam tas sekolah saya.

However:

Without saya, it can sound like a fragment, a note, or an instruction rather than a full, neutral sentence.
In simple, clear sentences (especially for learners), it’s better to keep the subject:
Saya menaruh buku ke dalam tas sekolah saya.

In casual conversation, if it’s already clear who is acting, people do often omit saya/aku.

Is there a single verb that means “to put something into” so I wouldn’t need ke dalam?

Yes, you can use memasukkan:

Saya memasukkan buku ke dalam tas sekolah saya.
= I put the book into my school bag.
Literally: I inserted/put-in the book into my school bag.

You’ll still often see ke dalam or just ke after memasukkan:

memasukkan buku ke tas
memasukkan buku ke dalam tas

Using memasukkan + ke (dalam) is very common when the idea is “put into.”

What level of formality does this sentence have? Would a child actually say it this way?

Saya menaruh buku ke dalam tas sekolah saya is:

Neutral–polite in form (because of saya and the standard menaruh).
Suitable for writing, narration, and formal or semi-formal speech.

A child or teenager in casual conversation is more likely to say something like:

Aku naruh buku ke tas sekolahku.
(colloquial naruh, informal aku and -ku, and often omitting dalam)

So the given sentence is perfectly natural, just slightly more “bookish” or neutral‑formal than everyday kid talk.

Does tas sekolah always mean “school bag”, like a fixed expression?

tas sekolah is a noun–noun phrase, where sekolah modifies tas:

tas sekolah = bag (for) school / school bag

This pattern is very common:

seragam sekolah = school uniform
buku sekolah = schoolbook
sepatu sekolah = school shoes

So yes, tas sekolah is naturally understood as “school bag,” not literally “bag school.”

How do I pronounce menaruh and tas sekolah? Where is the stress?

Indonesian stress is relatively light, usually on the second-to-last syllable in longer words:

menaruh → me-NA-ruh
- me as in meh
- na like nah
- ruh with a light h at the end; often realized with a slight glottal stop.
tas sekolah → TAS se-KO-lah
- tas like English tuss (short a)
- se like suh
- ko like koh (as in cold without the ld)
- lah with a light h at the end

Each vowel is pronounced clearly; there are no reduced vowels like English “schwa” in normal careful Indonesian speech.