Embrace New Beginnings
It's never too late to start. Your situations aren't you, but how you handle them. The years of sabbatical that you had to take can happen to anyone.
Hence, let's focus on what is left with you now. You have shared that you have already completed a certification recently and are looking forward to live projects. That makes you relevant and competent to apply for jobs.
The Advantage of Joining a Startup
Your decision to join a startup is excellent. At smaller firms, a fewer number of people handle a larger share of responsibilities. This opens up countless opportunities to grow beyond the defined job description.
Until it happens to you, look for projects online through portals such as Elance. A steady track record of work will build your strength.
Networking and Community Engagement
Connect with fellow techies in communities such as Stack Exchange and Quora. Try to contribute and help solve problems for others. In finding a solution for them, you will actualize your potential. It will also get you aligned with the mindset and work styles required in the workplace today. Picking up a catchphrase is easy; stay focused on current buzz.
Attend seminars and conferences relevant to your field. Initially, it might intimidate you to suddenly be exposed to a room full of people. Avoid comparing yourself to them. Just become a human sponge to soak in all the information and preparedness that you might see in them. Don't focus on making connections but build relations. Identify who is looking for what. You may not initially have anything to offer, but soon enough, you will be resourceful enough to support their growth.
Personal Branding and Mentoring
Read widely and blog in the areas of work you wish to take up. It's a very effective way to brand yourself. A resume is never enough. Blogging offers the quickest measure of your maturity over the subject and research.
You have already worked as a teacher; offer mentoring in areas that are your strength. It might seem natural to you. Mentor on any skill you can think of. Nothing is ever too small or insignificant. Even if you groom someone in effective communication, it counts. Mentoring is the fastest way to master skills as it requires developing a pattern for facilitating learning in others. In doing so, it will make you remain patient with yourself. Communities are the best place where you can look for people to mentor.
When you apply for a job, you may not put these things on your resume. However, it will build your job readiness far beyond what you can imagine.
Wish you all the best!