If they were the same age, I'd agree.
With the age range of the students, the teacher would need to teach 7 different subjects each lesson.
It's tricky but doable, to a degree. Not an ideal or acceptable situation.
My original idea of merging would, as an example, lead to 4 teachers and 76 students. Split the students into 4 goups of same or similar age and you have a much more satisfactory situation.