Yes, John and Emily are both deceiving themselves in thinking that they will able to finish doing well in their English class. It is a long way to go from a C or D to an A, and it would require more than just one project to bump their marks up in such an exponential way. It is something that happens often with many people, it is very easy to say to yourself that you will be able to do better if you put the work in. It gives them a sense of comfort in their lives in thinking that. But in reality, when it comes down to it, they will most likely procrastinate in doing the project, or not be able to complete it to their full potential because they will not have the time to do it. It is dangerous to rely only on the thought of thinking you will be able to do it.
The result of the schedule they are following will be overall negative. At high school age, it can be a very bad thing to overwhelm yourself with so many different activities. It draws you away from school and increases your level of stress in a huge way.
If they do not do well on their English project, they will very likely blame others before themselves. It is easy to blame the teacher’s marking, the project, how much time they were given, etc. In reality, they are all just excuses to make themselves feel better for not being able to plan out and manage their time better.
What I would do differently is plan ahead. Prioritize school before other things and take on additional activities only if they work around school. It is absolutely possible to have a busy schedule, as long as you plan ahead, and stay coordinated and on top of all your work and activities.