Here are some common English phrases and sentences that you can use in a school setting:
Greetings
* Good morning/afternoon/evening (formal)
* Hi, how are you? (informal)
* Hello, how's your day going? (friendly)
* Hi, what's up? (casual)
Introductions
* My name is [name], what's yours? (formal)
* Hi, I'm [name]. (informal)
* Can I have your name, please? (formal)
Basic Phrases
* Please, can I have [something]? (formal)
* May I help you? (formal)
* Excuse me, do you have [something]? (formal)
* I'm sorry, I didn't understand [something]. (formal)
* Thank you very much! (formal)
Asking for Help
* Can you help me with [something]? (formal)
* I need some help with [something]. (informal)
* Do you have a minute to help me with this? (formal)
Saying Goodbye
* It was nice talking to you. (formal)
* Goodbye, see you later! (informal)
* Have a great day/afternoon/evening! (formal)
Useful Sentences
* Can I have a pen/pencil, please? (formal)
* My book/materials are in my locker/bag. (informal)
* I lost my library book/bus pass, can you help me? (formal)
* The lesson will be on [topic] today. (formal)
* Have you seen [classmate] around? (informal)
* I'm going to the restroom/library/canteen during break. (informal)
Table Manners
* Thank you for the food/drink. (formal)
* May I have [more/less] of [something]? (formal)
* Can I have the bill, please? (formal)
* Keep your hands and feet off the table! (formal)
Other Useful Phrases
* I'm looking for [someone/something]. Can you help me? (formal)
* Can I make a phone call/ask a question? (formal)
* Is [event activity] today/this week? (formal)
* Can I go to the bathroom/step out for a minute? (informal)
Remember to always be mindful of your tone and language when communicating in a school setting. Formal language is generally more appropriate, especially when interacting with teachers or school administrators.