The SLS sessions last year were in late May and early June. If your finals week is at the end of school in late June like mine, you'll have a couple of weeks in between.
There's also a bit of downtime during SLS where you can study for your finals. I brought prep books for Calculus and Chemistry and worked through them during SLS, NASS, and the transit periods between the two.
Some schools will also give you a choice of taking your finals earlier, later, during the summer, or at the start of the next year. It really depends on what you can work out with your teachers and school administration.