Leaving playschool for a nursery seat, and they want a month's notice or a month's fee

Problem of the week: we confirmed her nursery admission for June at a bigger preschool near Madhapur. Paid, done. Then I told her current playschool she'd be leaving when their term ends this month. They've replied that the agreement needs one calendar month's written notice, so we either pay for May, when they're closed for summer anyway, or for June. I signed that agreement a year ago with a toddler on my hip and definitely did not read clause 9. Is this standard for playschools here? Did anyone push back and get it waived, or should I just pay and move on :)