J.W.
Being kicked out of school means different things, so you need to qualify your statement. He could be 'kicked out' for 3 days, 7 days, 10 days, or until you come to school to discuss the issue, or maybe worse yet for good because he brought a weapon of some sort to school.
Make good use of the school counselors and go talk with them, face to face, first without your son and then with your son and your husband in attendance. You need to find out what is causing his problems at school and you will probably get a hint of what's troubling him at home.
Most schools will not give him credit for classes if has 10 or more absences in a semester, so being kicked out of school can jeopardize his ability to graduate from high school. All the more reason to go talk with the school to find out the cause of the suspension. Could he be given an in-school suspension? Instead of sending him home (for many kids this is a reward for their bad behavior) they report to a classroom away from other students and doing nothing but reading and working on their studies. No interaction with others, lunches are eaten there, etc.
Teenagers in general are trying to cut 'the apron strings', establishing their own identities, their own routines, but they don't see the big picture and the consequences for alot of their actions. Consequences are not something they like, but they are a reality, such as suspension from school. This is a perfect opportunity to talk with your son about his high school diploma and what he'll be able to do without one, what are his options for employment, continuing education, living arrangements, etc. Most kids don't know the hidden costs of keeping a home together, realize what benefits they get by being your kid, such as health and dental care, cheaper car insurance to mention just a couple. There are consequences to active but ill informed sex life. Many teenage boys are sexually active, and Dad needs to have the consequences talk with him. If he's not going to school, doesn't have a job that can support himself, no health insurance, how will he support a partner, a child? If he were to contract a STD, how will he pay for treatment? and if he got so ill that he couldn't work, where will he get the money to survive?
Your first steps should be to get him back into school and off the streets. So go to school and start asking questions, listening and then work up a plan to get him back to school. The long term consequences of him not graduating from high school are devastating and costly for all involved. Based on what you're told at school, you probably need some family counseling as well. Mental health care is covered by your health insurance is Washington State as we have mental health parity, meaning you can go see a mental health (counselor) practioner for the same co-pay as any other specialist doctor.
I wish you all well.