Learn Spanish (Latin America): Dieciséis chicos y dieciocho chicas están en la escuela. - Sixteen boys and eighteen girls are in the school.

Dieciséis is made by combining diez y seis (ten and six) into one word. When you combine them, the natural spoken stress of the word shifts. To make sure we still pronounce the seis part with emphasis, Spanish spelling rules require an accent mark over the 'e'. Dieciocho (ten and eight) doesn't need one because its natural stress already falls on the correct syllable (the first 'o' in ocho).

Wait, diez ends in 'z'. Why do dieciséis and dieciocho use a 'c'?

In Spanish spelling, the letter 'z' is almost never followed by an 'e' or an 'i'. When diez combines with y (which changes to an 'i' in these compound words) to form numbers like dieciséis (16) or dieciocho (18), the 'z' changes to a 'c' to follow this spelling rule.

Why do we use están instead of son for "are"?

We use están (from the verb estar) because the sentence is talking about physical location—where the boys and girls are right now (en la escuela). The other verb for "to be" is ser (which would be son here), but that is used for permanent traits, identities, or descriptions, not locations.

I've seen chicos used for "kids" in general. Does it just mean "boys" here?