It reads fine, but it's a bit wordy. Maybe this?
If Miriam Middle School students weren't excited about the gravity project, they certainly were on Friday afternoon.
How can I make this sentence better, or is it OK?
If students at Miriam Middle School weren’t excited about their upcoming gravity project, they were after school Friday.
3 answers
Or is there another word you could suggest rather than certainly? I'm going based off their reaction.. Maybe seemingly?
You could use “sure” or “surely” instead of “certainly.” Any of those 3 will work.