Upacara is a noun, why there is no 'punya' needed here?
'punya'= to have, to possess , it's not used as a modal verb in Indonesian, it's used to show ownership.
If you want to use a verb in this sentence, you can use something like 'mengadakan' / 'melakukan'.
Terima kasih bagi penjelasan anda
Isn't "we have a ceremony" ownership?
"Kami (meng)gelar upacara" should be correct. "Kami upacara" (without the verb) is only used in informal setting.
Kami memeliki upacara di halaman sekolah ini benar