I attended SLE this past year and I went session 2 from June 10th- June 16th. The application is more relaxed than you may think it is, it is comprised Candidate Questionnaire and your workshop preference (Don't count on getting your top workshops when you go there, I put Kinesiology last on my preference and I got it first). During the Candidate Questionnaire, they will ask for SAT and ACT scores (Honestly, just do your best and you'll be fine). But surprisingly they do not ask for GPA. When I attended this past year they said that GPA isn't the main focus point on your application every school rates GPA differently (in terms of a 4.0 or 5.0 scale) In my opinion, get involved in your school and go for leadership positions and try to excel on your SAT and ACT. There is this one candidate in my squad who had a 35 on his ACT and I also met candidates who had 17s -24s on their ACT. But the people who had lower test scores were mainly athletes or people that held amazing leadership positions. Me, personally, I got a 1250 on my SAT(its about average) and a 29 on my ACT(a little bit better than average) but I hold a pretty good leadership position in my schools band (Marching Tech). Just do your best get leadership positions and shoot for as high as possible on the SAT/ACT and you'll be fine.
Good luck on your application!