am I to blame?

I got a Saturday detention for 'pushing' someone and texts from a month ago. I. The text they see that I 'called' her fat and said she had FBS so they gave me detention. And yesterday they forced me to say I 'pushed' her, it seems like they wanted me to say it and they told me to stay away so now they're looking at texts from may 19 and they're gonna give me detention this Saturday. Tomorrow I'm going in with my dad and he'll be defending me bc nobody can stick up for me in school. Does this seem fair? What should I do? What happens when you get a Saturday? I know she's trying to get me in trouble the last 13 days of school and it's ridiculous!