According to Techcrunch, Preply, which has built an online marketplace for finding and booking private tutors for a range of subjects, has closed a $1.3 million seed round. It supports booking of both in-person lessons in a chosen location and also remote tutoring, via a video chat.

Investors in Preply's seed round include Arthur Kosten (ex-CMO at Booking.com), Polish VC RTAventures, and founder & CEO of DocPlanner, Mariusz Gralewski.

The team launched its tutoring marketplace back in April 2013, before going through the TechStars Berlin program. It's currently operating in five markets: Poland, Ukraine, Russia, Mexico and Brazil, and is prepping to launch in three more: Germany, UK, and Spain -- using the new financing to fund this international expansion.

The seed round will also be used to develop products for teachers and students using its platform -- and it will be expanding its dev team to build out core functionality.

Preply does not offer its own videoconferencing tech -- rather its tutors offers lessons via third party tools like Skype (which it anticipates integrating with via an API in future). Instead it says it has focused on structuring its marketplace -- including by adding a ranking algorithm that uses machine learning for recommendations and classification of tutors, based on their profiles.

A detailed user reviews and ratings system feeds into this recommendation algorithm. There's also a (manual) verification process for tutors, with verified tutors having a badge displayed on their profile.

'We define customer satisfaction as our primary metrics, so our main criteria are customers' reviews. For each tutor, we measure how he or she can motivate the student, soft skills, strictness, methodology, punctuality and overall effectiveness measured as each student self-assessment as separate metrics. All of that combined produces self-learning ranking algorithm that pushes the best tutors up and meanwhile enables 'young stars' (new tutors without students) still to be visible and be able to get new students,' it says.

Preply says it's generating revenue from more than 130 countries via its marketplace at this point. Its business model involves taking all revenue from the first lesson booked via the platform, as a lead generation fee, then taking a revenue share of any lessons booked thereafter. It's not currently breaking out what the revenue share is.

It has more than 25,000 tutors signed up to offer teaching services via the marketplace at this stage, and more than 70,000 students registered. Languages are the most popular categories, although the marketplace is not exclusively focused on this (unlike, for example, tutoring platform Verbling) -- offering tutoring in other subjects including art, science, maths and music.

Tutors are free to set their own prices, although the marketplace has a fixed $2 minimum. Some 10,000 hours of classes are given each month, after booking via the platform, according to the startup.

'Step by step local tutoring is going to online,' Preply argues, pointing to the pull factors of lower organisational costs, access to global knowledge and arbitrage between countries, allowing for students to choose a less expensive tutor who is able to offer lessons at a lower price because they live in a different part of the world.

'Both local and online tutoring markets are not taken globally so far. This means that the next 3 to 4 years we will witness an interesting competition among the existing platforms and probably new one to lead the market,' it adds.

There's no doubt online tutoring is a very crowded space already, with multiple platforms in play -- but that's a measure of how much demand (current and future) is being seen here. In terms of specific competitors, Preply names US-based Wyzant and Takelessons as its 'strongest' rivals, reckoning they will definitely look to grow their business internationally at some point.

'We believe that we have a very strong technical team and early focus on international markets rather than the U.S. only that will help us compete with these well-established players,' it adds.