Summer Session as a HS Junior

Hello. For the upcoming summer, I am considering attending Session A of the Summer Sessions at UCLA. I’ve always loved the campus and would not mind taking some college-level classes to further my education and prepare me for college.

a. How many units/classes are manageable during the summer?

b. Also, I am a little concerned about the social aspect of the Summer Sessions as a junior in high school. Is anyone aware whether high school students typically attend the Summer Sessions? I do not think college students will necessarily want to hang out with a high school student? Though my focus is on the academics for the summer, friends would be nice lol.

Thank you !!!