Homework Causing Conflict With Parents?

The school year is almost over for me, and there are an endless amount of projects! I have been bringing people over to my house for the last 3 days working on a project. Now that it's finally done today, I have to go to someone else's house to do another project. Not to mention, I have been also staying up late finishing my individual projects for school. My parents think that I'm lying or just playing when I'm not! I tried explaining to them and all they do is start yelling and say that I join too many extra-curricular activities! Why don't they every listen! What can I do so they believe me?