One of your challenges for your business model might be to ensure long-term engagement. Parents might be very interested in your product but might lose interest after a while, leading to high churn rate after a few months. How are you dealing with this? Any tips for other startups who are also selling to parents?
Your app reminds me of Google’s Read Along [0], which is also a reading tutor for young children which one of Google’s offline speech recognition systems (it seems they are currently using an RNN-T encoder-decoder architecture with wordpieces as the base unit). Too bad this app was not marketed properly and translated in many languages, a missed opportunity it seems!
Soapbox Labs [1] is providing a speech recognition API (also offline) for reading tutors and other apps. It might be cheaper to integrate their technology? I believe their ASR technology used to be based (or still is?) on the Kaldi speech recognition toolkit, that might ring a bell ;-)
[0] https://play.google.com/store/apps/details?id=com.google.and... [1] https://www.soapboxlabs.com/