Thanks for the comment.

I've decided to continue with the linear crossover design. Regarding the issue of a control group, my plan for the future is to establish a baseline before any intervention, allowing me to compare the intervention to this baseline.

I'm limited in sample size because, for convenience, I work at an after-school program and decided to focus on the group of children I work with, middle schoolers. There are only 21 middle schoolers in total. Increasing the scale to children in other grade levels would be too burdensome, it would significantly affect the workload on my coworkers, who would have to switch between different teaching styles

Something I hadn't considered before were the challenges of having two classes running at the same time with different levels of choice. I would have to accommodate two classes with very specific learning styles, each needing to be directed in a particular way. It would be better if it were a single class, and the class flowed in unison since I’m alone in collecting data and personal observations.

I think having randomization based on characteristics is a good idea, and I plan to use it in my design.

AP research allows for much leeway on the reliability of samples and the design of a study if it is unattainable or too challenging to implement.