What are some strategies for adjusting my pacing when students need more time to grasp key concepts?

Each September, at the end of our unit on the five senses, my team has “Apple Day” where we use apples to help investigate our five senses. I love science and STEM, so I’d like to do something in those areas. I usually have students investigate if apples sink or float, but I’d like to change things up this year. Any ideas?

Does your district operate under a modified calendar? What is your start and end date? What would your ideal school year calendar look like?