In this case, you write a greeting in the renrakucho a little while after enrollment. This model will be suitable if you didn’t write a greeting at enrollment.
Conversational flow and useful expressions
Your child’s behavior
How your child is getting on and your thoughts as a parent
Phrases such as「いつもありがとうございます」(itsumo arigato gozaimasu) or「お世話になっております」 (osewa ni natte orimasu) are used at the beginning here. They are more polite than 「お世話様です」(osewasama desu) or 「おはようございます」(ohayo gozaimasu). If your child has only recently started school, a politer phrase would be more suitable. You can switch to osewasama desu or ohayo gozaimasu as you grow accustomed to the school.