As a response to the lack of authenticity and meaningfulness of a techniques-centred approach to sport within physical education, Siedentop (1994) developed "Sport Education". The overriding goals of this pedagogical model are the development of competent, literate and enthusiastic sportspersons (Siedentop et al., 2011). Reviews of research on Sport Education (e.g., Hastie et al., 2011; Wallhead and O'Sullivan, 2005) have reported varying degrees of accomplishment of these goals, to the point now where Hastie (2012, p. 10) suggests the following executive summary: "evidence for competency is 'burgeoning and developing', support for literacy is 'emerging', and that enthusiastic responses by students have been 'significantly substantiated".
According to Wallhead and O'Sullivan (2005), research on Sport Education as a pedagogical model has been framed according to two broad categories: practical strategies required to implement Sport Education (pedagogical strategies, assessment, model application to different areas, etc.) and the educational impact of this model on various dimensions of student learning. With respect to the second of these (Sport Education's educational impact), research findings have suggested consistent results according to students' personal and social development, namely their attitudes (enthusiasm, motivation, etc.) and values (affinity, equity, etc.) (Hastie et al., 2011; Wallhead and O'Sullivan, 2005). These findings are reflected by teachers' (Alexander et al., 1996; Strickwerda-Brown and Taggart, 2001) and students' (Bennett and Hastie, 1997) perceptions as well as empirical measurement (Hastie, 1998b).
Nonetheless, research is still sparse with respect to the model's impact on student learning outcomes (Hastie et al., 2011). This issue is particularly important given that learning is one of the central goals of education, which means that the substantive value of the motor task cannot be underestimated at the expense of group activities and social interaction. The personal and social domain cannot therefore become an end in itself, and it is through the motor task, the pursuit of competence and performance that physical education becomes meaningful (Mesquita, 2012). Therefore, the purpose of the present study is to scrutinize what is currently known concerning students' learning when participating in Sport Education in order to make judgments and directions that future research and practice might follow.
Systematic search and study selection
A systematic literature search was conducted using seven databases, namely Academic Search Complete, ERIC, SPORTDiscus with Full Text, PsychInfo, Education Research Complete, ISI Web of Knowledge and SCOPUS. This search was conducted from their inception to September 20, 2013 using the "Sport Education" as the keyword, and performed by two researchers with experience in this methodology and knowledgeable of instructional models in physical education.
Using these, studies for this review were included according to the following criteria: (i) were published in peer reviewed international journals; (ii) included at least one group participating in a Sport Education season; and (iii) focused on student's learning outcomes (skill development, knowledge, tactical awareness and game play). Review and opinion articles, articles focusing on personal/ social outcomes, and articles focused on the discussion of the practical strategies required to implement Sport Education (pedagogical strategies, assessment, etc.) were excluded from this review.
Figure 1 presents the summary of decisions taken for identifying studies. Initially, from the wide range of articles that identified "Sport Education" in either the title, abstract or keywords (n = 36,954), only those related to Sport Education research were selected for reading (n = 276). From this number, only peer-reviewed articles related to students' learning outcomes (skill development, knowledge improvement tactical development and game play) were selected (n = 34). Review articles (n = 2) and articles without full text (n = 9) were excluded for this review. Therefore, only peer review journal articles that specifically studied students' improvements according to skill development, tactical development or game play were included to the present review (n = 23).
In order to analyse all the information from the 23 articles included in this review, content analysis was performed. The following categories were defined a priori using the method suggested by Harris et al. (2013): purpose, type of study, dimension of learning analysed, participants/setting, data collect/analysis, and principal results.
Assessment of study quality
The 23 studies that met the inclusion criteria were assessed for quality. These criteria were adapted from the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) recommendations (Vandenbrouck et al., 2007) and the Consolidated Standards of Reporting Trials (CONSORT) statement (Moher et al., 2001). A formal quality score for each study was completed on a six-point scale by assessing a value of 0 (no present or inadequately described) or 1 (present and explicitly described) to each of the following questions: (a) Did the article provide a detailed description of the program context: teacher expertise and students previous experience? (b) Did the study report sources and details of outcome assessment? (c) Did outcome assessment instruments have acceptable reliability for the specific age group? (d) Did the study report the precise details of the interventions intended for each group and how and-when they were actually administered? (e) Did the study report the fidelity of the intervention that was delivered to participants and was the delivered content in the true nature of the intended intervention? (f) Did the study report the effect size of primary and secondary outcome investigation? Studies scored from 0-2 were classified as "low" quality studies, from 3-4 as "moderate" quality studies, and those that scored 5-6 were classified as "high" quality studies. This assessment was performed by one of the authors of the present article as well as an external reader who had significant research in instructional models in physical education, particularly Sport Education. In order to measure the degree of reliability of the two assessments, the Cronbach's alpha was calculated. This test showed a higher agreement between the two assessments ([alpha] = 0.99). The assessment of studies' quality is presented in Table 1.
Table 2 show the 23 articles that were included in this review. The assessment of the study's quality is included in the table.
Source, grade and sport
Sport Education research considering students' learning outcomes is particularly diverse, spanning a variety of countries, the school grade in which the season was applied, and the sports studied. According to the country where the Sport Education season took place, the most frequent country was Australia (n = 7), followed by USA (n = 5), Russia (n = 2), Portugal (n = 2), Hong Kong (n = 2), Spain (n = 2), United Kingdom (n = 1) and New Zealand (n = 1). With regard to the grade level used, the most frequent were those most associated with middle school (sixth through eighth grade; n = 14), followed by high school (ninth through twelfth grade; n=7) and finally elementary school (first to fifth grade; n = 4). Team sports were the most commonly studied (n = 19), whereas only four studies incorporated individual sports (such as athletics, badminton) or dance in their seasons.
This research spans two distinctive methodological approaches: qualitative studies (students' and teachers' perceptions) or quantitative studies (quasi-experimental, pretest-posttest design). From Table 1 it can be seen that qualitative research has focused on three concerns: teachers' perceptions, students' perceptions, and studies that have examined both teachers and students. Four studies focused on the perceptions of teachers concerning students' learning (Alexander and Luckman, 2001; Carlson and Hastie, 1997; Curnow and McDonald, 1995; Grant, 1992). Several authors (n = 6) examined both students' and teachers' perceptions (Alexander et al., 1996; Calderon et al., 2010; Carlson, 1995; Clarke and Quill, 2003; Cruz, 2008; Li and Cruz, 2009;) and only one study has analysed students' perceptions (Gutierrez et al., 2013). In these studies, several tools were used to examine the perceptions of the participants such as formal and informal interviews (n = 11), reflective diaries (n = 7), questionnaires (n = 3), drawings (n = 1), and group interviews (n = 1).
In studies following qualitative measures, quasi-experimental pre-posttest designs (Cho et al., 2012; Hastie and Trost, 2002; Hastie et al., 2009; 2013; Mesquita et al., 2012; Pritchard et al., 2008) have been used in order to analyse the impact of Sport Education on students' learning outcomes. The most frequently used instruments in these designs were skill tests (n = 6), followed by tactical knowledge tests (n = 4) and systematic observation instruments to evaluate students' improvements (n = 3), such as the Game Performance Analysis Instrument (Oslin et al., 1998).
Mixed methods (incorporating both quantitative and qualitative assessment) were also used (Brock et al., 2009; Browne et al., 2004; Hastie, 1998a; 1998b; Hastie and Curtner-Smith, 2006; Hastie and Sinelnikov, 2006). The majority of these studies used both lesson videotapes and interviews (n = 4). Field notes (n = 1), questionnaires (n = 1), self-evaluation of skills (n = 1), critical incidents (n = 1), game design forms (n = 1) and tactical quizzes (n = 1) were also used. In these mixed methods studies both students' learning (through empirical measurement) and students'/ teachers' perceptions (through more qualitative measures) were examined.
Dimensions of students'...