Sometimes the usage of preposition "in' and 'at' is very confusing and may cause errors when they are used in sentence. Here are tips on using these two preposition which I quoted from The Star, 19 August 2010, written by Fadzilah Amin.
'At' is used when the school is named. For example, 'I am studying at Sekolah ABC'.However, either 'at' or 'in' can be used when saying a child is still attending school, e.g. "My daughter is only 16 and still in/at school".We can also use either when talking about certain school activities or phenomena, like 'sports in/at school' or "bullying in/at school'.
Other language tips.....
The word 'to' belongs to two different word classes or parts of speech. When used in 'to sing','to play', etc, it is an infinitive marker and is used with the base form of the verb (without the -ing) in sentences like 'I like to sing/play'. But 'to' can also function as a preposition before nouns, pronouns, noun phrases and gerunds, which are -ing forms of verbs functioning as nouns.
In 'I'm looking forward to meeting you', 'meeting' is a gerund. The 'to' before it is a preposition , not an infinitive marker. So it can be used before a gerund.
Common Errors...
Urinate is not allowed in the bathroom ------ Wrong
Urinating is not allowed in the bathroom ------ Correct
Please flush water after used ---------- Wrong
Please flush the toilet after use ----------- Correct
Do you remember when you feel it? -------- Wrong
Do you remember when you felt it ? --------- Correct
Do you know why you choose it ? ----------- Wrong
Do you know why you chose it ? ------------ Correct