"Peter is near that school."
Translation:पीटर उस स्कूल के पास है।
Like English prefers subject-verb-object constructions, Hindi prefers subject-object-verb constructions. Since 'Peter' is the subject of the sentence, the correct translation is पीटर उस स्कूल के पास है. That said, you can sometimes change word-order in spoken Hindi to place emphasis on different words. For instance, when asked who is standing near the school, you could say उस स्कूल के पास पीटर है to emphasise that it is Peter (and not anyone else) who is near the school.
उस is the indirect form of वह to be used in the oblique case (when it is the object of a postposition).
The noun phrase 'वह स्कूल ' in the sentence is followed by a postposition 'के'. This means it is in the oblique case. 'वह स्कूल ' becomes 'उस स्कूल' in the oblique case which is why the latter must be used.
The 'case' of a word can be understood to be its form that is dependent on its position and function in a sentence. In practice, there are three main cases that a noun or noun phrase can be in.
i) Direct case - This is the 'simple' (or default) case in which the noun phrase appears most often.
ii) Vocative case - The case that a noun is in when it is being directly addressed (Eg: अरे बच्चे ! - Hey kid! - बच्चे is in the vocative case which can be compared to the direct case form 'बच्चा')
iii) Oblique case - This is when the noun/noun phrase is the object of a postposition. For example, in the sentence "I went to my old school yesterday", the noun phrase "my old school" is the object of the preposition 'to'. Similarly, in the Hindi sentence 'हरे डिब्बे में खिलौने हैं' (There are toys in the green box), the noun phrase 'हरे डिब्बे' is the object of the postposition में and is therefore in the oblique case (compare with the direct case form हरा डिब्बा ). The oblique case is actually composed of seven different cases depending on the type of the postposition but this distinction is only important in the case of pronouns.