As a majorly qualitative methodology, this research appealed to participant observation, documentary analysis, focus groups, and a learning styles test. The following instruments were used to carry out this investigation:

VARK test (Visual, Auditory, Reader/Writer, and Kinesthetic). The version developed by Fleming & Mills (1992, as cited in García,2007) was useful to find out whether Duolingo would be an appropriate application to use in the intervention.

Table 1

RESEARCH TECHNIQUE	PARTICIPANTS	MEN	WOMEN
VARK test	238	67	171
Participant observation	200	60	140
Documentary analysis	200	60	140
Focus groups	80	30	50

Action research is regarded as an inclusive methodology in which all those individuals interested in overcoming a status quo or facing a problem must participate (Carr & Kemmis, 1986; Stringer, 2007). For such a reason, the study appealed to comprehensive sampling (Ary et al., 2010); this meant for every student using the mobile app Duolingo to be included. Participants were informed that the inquiry involved no risks at all since the use of the application contributed to the overall foreign language learning process.

Thus, all teenagers who are part of the teacher-researcher’s classes were taken into account, that is, 367 learners. Unfortunately, not all of them had the opportunity to use Duolingo since many did not have internet at home, or their technological devices did not support the software because of technical reasons. This justified thes ampling strategy, where only 200 students were included, 140 women and 60 men, between 14-17 years of age.

The procedure followed processes that were adapted to the context needs and emergent social situations. During June 2021, a reflective diagnosis was conducted on the teacher-researcher’s educational practice regarding English language teaching. In this sense, a record was made doing participant observation and documentary analysis, such annotations were useful to carry out a first analysis of information through initial, focused, and axial coding (Charmaz, 2006).

In a second moment, an action plan was created including three strategies: 1) learning styles diagnosis; 2) selection of a mobile app to learnEnglish; and 3) application and follow up of the intervention throughout the first semester of the school year 2021-2022. Again, participant observation as well as documentary analysis were conducted to analyze data with initial, focused, and axial coding.

Finally, eight focus groups were organized to evaluate the intervention during November 2021. Likewise, participant observation and documentary analysis complemented more grounded results and an establishment of a hypothesis related with the use of mobile phone apps to improve English language learning in high schoolers. Through out the research, data analysis was conducted using a digital word processor (Microsoft Word), which is valid in qualitative analysis (Watkins, 2017).

The VARK questionnaire was applied to 238 learners (Table 2), but even when everybody was taken into account, quite a few adolescents simply did not want to take the test and others did not have the technological infrastructure at home to do so (internet, computer, or cell phones). Also, it is important to mention that not all students who answered the instrument used Duolingo.

Table 2

LEARNING STYLE	PARTICIPANTS RESULTS	MEN	WOMEN
Visual	52 (21.84%)	16 (6.72%)	36 (15.12%)
Auditory	68 (28.57%)	20 (8.40%)	48 (20.16%)
Reader/writer	40 (16.80%)	10 (2.20%)	30 (12.60%)
Kinesthetic	78 (32.77%)	21 (8.82%)	57 (23.94%)

Test results showed that most students obtained a kinesthetic learning style. Auditory learners were second, visuals third, and reader/writer styles were last. These findings suggested a compatibility with the strategy of using Duolingo to strengthen English language education processes.

Different mobile phone applications like Duolingo, Hello English: Learn English, and Aprende Inglés gratis! were evaluated before selecting one. Having compared the apps, Duolingo was chosen since it has approximately eighty million users worldwide; in addition, it sets goal sand time to administrate study (Bustillo et al., 2017). Another very important didactic element was diagnostic, formative, and summative evaluation for which the app applies several exercises that constantly measure learning. Moreover, this software makes use of various resources aswell as dynamics; for example, gamification, images, listening, and interpretation activities.

The Duolingo platform was used to create groups and administrate learning activities (Figure 2). One of the main advantages of this application is that teachers can organize pedagogical processes on the website, which allows a personalized follow through by assigning specific tasks to each group. At the same time, learners are able to share progress and achievements with educators.

Figure 2 Source: retrieved from the platform Duolingo for schools.

Since Duolingo models the pronunciation of vocabulary and challenges to identify words, many participants reported to have developed a capacity to comprehend phrases in spoken discourses in movies and TV shows. Next, an answer provided by a student makes this evident:

Like in other studies conducted through out the pandemic (Hidayati et al., 2021), the students showed a significant improvement in their vocabulary when using Duolingo. Some aspects which influenced this appreciation were that, according to responses, learners had opportunity to review lessons and interact with words in a fun way as this application would give them symbolic rewards every time progress was made. A participation during the focus group pointed out such an aspect:

Another great option offered in Duolingo is that the comprehension of certain grammatical topics is reinforced. In this sense, some adolescents showed more participation during classes acknowledging they had done better by practicing their English in the mobile phone application. Next, a commentary on such appreciation:

The practice activities provided in Duolingo are similar to certain exercises that adolescents have to answer in institutional evaluations. Therefore, a few learners reported they felt that the tests had been easier; as a matter of fact, the documentary analysis permitted to observe how more students were getting better grades, and some of the ones who were failing were passing. A student stated on this aspect:

In order to incorporate all participants’ perspectives, answers in focus groups were grouped according to the categories described before: listening comprehension, vocabulary acquisition, understanding of topics, and exam scores. Now, qualitative research is characterized by being narrative, dialectical, and making evident feelings of learners as well as understanding of problematics, but this investigation design falls under thecritical educational science where other methods of analysis may be incorporated (Ary et al., 2010; Carr & Kemmis, 1986; Stringer, 2007). Thus, percentages were calculated in consonance with the concurrences for each category. Such numerical information intends to include responses made by 80 students (Figure 3), and in no way has the purpose of measuring any variable like in a quantitative study.

Figure 3 Note: the image reflects responses made by 80 students in focus groups.

In order to include all 200 students, the information from participant observation records and documents part of the teacher-researcher’s daily responsibilities were put together with data analyzed in focus groups by incorporating the coded units of analysis into each of the main categories. Figure 4 shows the appreciation on how Duolingo impacted high schoolers’ English language learning experience.

Figure 4 Note: this graph includes interpretation of observation records, documentary analysis, and focus groups including 200 learners.

Thereupon, as part of the qualitative tradition, it can be hypothesized that using M-learning with apps such as Duolingo ameliorates learners’ educational experience. Also, English language education is enhanced through the appsince it incorporates a gamification environment which makes learning a positive experience; plus, it helps to develop listening comprehension skills, vocabulary retention, understanding of topics, and it supports preparation for certain exam exercises. However, as education is context specific these findings are in no way generalizable, but researchers are invited to evaluate whether their conditions are similar to the present in order to use this application in their classroom settings.

During the intervention, some students argued about not having enough room on their cellular phones to install the application. This issue was addressed by providing them with Duolingo’s web address so that they could carry out learning activities. However, such a situation did not cease to be a problem since the same excuse continued to be presented by a few high schoolers.

Contrastingly, Munday (2016) conducted an investigation with the aim of seeing if this mobile app could be employed in a language course following the same idea of ubiquity, which in turn would serve as a complementary activity to learners’ language acquisition. The expert also used the web address as an alternative to provide more accessibility options. Subsequently, the researcher observed how few students decided to continue using Duolingo as an independent learning strategy as they saw it to be useful, an aspect as well identified by other authors (Nushi & Hosein-Eqbali, 2017).

Those students who had trouble entering the groups showed their cell phone to demonstrate the case. As a solution, they were asked to answer the app without acces sing the Duolingo group, and progress was registered manually in attendance lists. It is worth mentioning that very few mobile devices presented such problems, but it was clear how this software was not compatible with every single device.

There were few cases in which the Duolingo system did not report progress of a few learners who met learning goals set through the platform. Additionally, for some reason the website that allowed monitoring application stopped working. This issue was faced by asking pupils to present their mobile device with progress, and again achievements were registered manually in attendance lists.

Unfortunately, the due to covid-19 social lockdown forced all of Mexico to suspend face to face educational activities. Throughout this moment, the digital divide was more evident than ever; many high schoolers argued that they had no internet or that their cell phones could not operate Duolingo. Even though the application is free to use, it requires online connectivity. In extreme cases, those students who did not have the chance to utilize app at all were given a follow up with teaching-learning assignments implemented regularly. These juveniles in specific were discarded from this intervention without affecting them academically.

In a study carried out by Habibie (2020) and Kenny (2014), such a requirement of online connectivity weakness was also identified; furthermore, these experts state that certain activities cannot be conducted on both PC and smartphones. Hence, the solutions tried throughout this intervention may not have contributed to solving the digital gap, but they looked forward to avoiding exclusion of learners in the learning and evaluation process.

Likewise, research conducted by Nadhifah & Puspitasari (2021) demonstrates the effectiveness of M-learning during the confinement period as a self-learning strategy with the help of Duolingo. Their investigation revealed how high schoolers felt pleased because not only was the application easy to use, but it as well helped them to acquire skills to formulate expressions in English. Nevertheless, the app seemed quite useless for those learners, whose level was labelled as intermediate or advanced.