The Class Size Controversy

[Excerpt] When we ask whether class size matters for achievement, it is essential to ask also, how class size matters. This is important for three reasons. First, if we can observe not only achievement differences, but also the mechanisms through which the differences are produced, this will increase our confidence that the differences are real, and not an artifact of some unmeasured or inadequately controlled condition. Second, the effects of class size may vary in different circumstances, and identifying how class size affects achievement will help us to understand why the effects of class size are variable. Third, the potential benefits of class size reduction may be greater than what we observe. For example, suppose class size reductions aid achievement, but only when teachers modify instructional practices to take advantage of the smaller classes. If a few teachers make such modifications, but most do not, then understanding how class size affects achievement in some cases will help reveal its potential effects, even if the potential is generally unrealized

School Disciplinary Climate: Characteristics and Effects on Eighth Grade Achievement

Seven dimensions of school disciplinary climate were identified based on a representative sample of grade 8 students in the United States. Within schools students varied considerably in their perceptions and experiences about discipline. The variation was related mainly to students' socioeconomic status (SES), sex, and ethnicity. There was a significant contextual effect of school mean SES on disciplinary climate, larger titan the individual effect of SES. Schools with primary or intermediate grades tended to have more favorable disciplinary climates titan either junior or senior high schools. School location had small effects on disciplinary climate. The disciplinary measure with the strongest relationship to academic achievement pertained to classroom disruption.A partir d'un échantillon représentatif d'élèves de la 8e année aux Etats-Unis, sept dimensions du climat disciplinaire d'une école ont été identifiées. Les perceptions et les expériences des élèves quant à la discipline variaient beaucoup, surtout en fonction de leur statut socio-économique, leur sexe et leur ethnicité. L'effet du statut socio-économique était plus significatif quand Von calculait la moyenne pour l'école que quand l'on tenait compte du statut d'un individu. Les écoles primaires avaient des climats disciplinaires plus favorables que les écoles secondaires (premier ou deuxième cycle). L'emplacement de l'école avait peu d'effet sur le climat disciplinaire. La mesure disciplinaire qui avait le plus d'effet sur la réussite académique était liée aux comportements perturbateurs

The International Adult Literacy Survey: Implications for Canadian Social Policy

Results of the first (1994) International Adult Literacy Survey show a dispro- portionate number of Canadians scoring at the high and low ends of the scales used in the study. We outline three significant Canadian results; examine their implications for educators and policy makers; propose a number of interventions to support literacy learning, especially for families from low socio-economic back- grounds; and argue that a concerted effort by schools, communities, families, and governments is essential for literacy skill development throughout life. Les résultats de la première enquête internationale sur l’alphabétisation des adultes (1994) indiquent un nombre disproportionné de Canadiens se situant aux ex- trémités supérieures et inférieures des échelles d’évaluation utilisées dans cette étude. Les auteurs présentent trois résultats canadiens significatifs, analysent leurs implications pour les enseignants et les décideurs, proposent plusieurs interven- tions en matière d’alphabétisation, notamment pour les familles défavorisées sur le plan socio-économique, et affirment la nécessité d’un effort concerté de la part des écoles, des familles et des gouvernements pour le développement de la littératie tout au long de la vie.

Equivalence of Testing Instruments in Canada: Studying Item Bias in a Cross-Cultural Assessment for Preschoolers

Item bias, which occurs when items function differently for different groups ofrespondents, is of particular concern to cross-cultural assessments. It threatens measurement equivalence and causes intergroup comparisons to be invalid. This study assessed item bias among francophone, anglophone, and Aboriginal preschoolers in New Brunswick, Canada. We used data from the Early Years Evaluation-Direct Assessment (EYE-DA), an assessment tool that measures children’s early educational development. The analytical approach used to investigate item bias is called differential item functioning (DIF). This study offers an application of DIF analysis that combines statistical testing and graphical representation of DIF. Analyses yielded consistent results revealing that linguistic and cultural differences between francophone and anglophone children are more challenging to achieve transferability than cultural differences between Aboriginal and anglophone examinees

The Environmental Effects of Global Changes on Northeast Central Europe in the Case of Non-Modified Agricultural Management

Climate impact scenarios for agriculture usually consider yield development, landscape water balance, nutrient dynamics or the endangerment of habitats separately. Scenario results are further limited by roughly discriminated land use types at low spatial resolution or they are restricted to single sites and isolated crops. Here, we exemplify a well data based comprehensive sensitivity analysis of a drought endangered agrarian region in Northeast Germany using a 2050 climate scenario. Coherently modelled results on water balance and yields indicate that agricultural production may persist, whereas wetlands and groundwater production will be negatively affected. The average percolation rate decreases from 143 mm a-1 to 12 mm a-1, and the average yield decline broken down by crops ranges from 4% for summer wheat to 14% for potatoes (main cereals: 5%)

Test of a DC-HTS Busbar Demonstrator for Power Distribution in Hybrid-Electric Propulsion Systems for Aircraft

In the framework of the German project TELOS (Thermo-Electrically Optimised Aircraft Propulsion Systems) a high-temperature superconducting 40 MVA DC demonstrator busbar for hybrid-electric propulsion systems for aircraft has been developed. The design current for a temperature below 25 K is 13.3 kA and the rated voltage is 3 kV. The 2-pole busbar contains 2 stacks of REBCO coated conductors which are supported by a 3D-printed structure allowing compensation of thermal length changes of the superconductor. It fits in a cryostat tube with an inner diameter of 25 mm. A special focus has been put on low-resistive joints that are necessary to connect single elements of the busbar system. The special layout of the joints allows an effective current redistribution between the different tapes in a stack. We present results for the test of the DC busbar demonstrator in liquid nitrogen at 77 K. The design current for this temperature is 3.3 kA which corresponds to a rated power of 10 MW. We applied currents up to 3.5 kA and measured the I-V characteristics and contact resistances of 90° and 180° joints in a virgin and in a strained state thus simulating thermal length changes. We also present results of Lorentz-Force tests with short AC current pulses up to 20 kA to demonstrate the viability of the design for application with currents up to 13.3 k

Tritium supply and use: a key issue for the development of nuclear fusion energy

Full power operation of the International Thermonuclear Experimental Reactor (ITER) has been delayed and will now begin in 2035. Delays to the ITER schedule may affect the availability of tritium for subsequent fusion devices, as the global CANDU-type fission reactor fleet begins to phase out over the coming decades. This study provides an up to date account of future tritium availability by incorporating recent uncertainties over the life extension of the global CANDU fleet, as well as considering the potential impact of tritium demand by other fusion efforts. Despite the delays, our projections suggest that CANDU tritium remains sufficient to support the full operation of ITER. However, whether there is tritium available for a DEMO reactor following ITER is largely uncertain, and is subject to numerous uncontrollable externalities. Further tritium demand may come from any number of private sector “compact fusion” start-ups which have emerged in recent years, all of which aim to accelerate the development of fusion energy. If the associated technical challenges can be overcome, compact fusion programmes have the opportunity to use tritium over the next two decades whilst it is readily available, and before full power DT operation on ITER starts in 2035. Assuming a similar level of performance is achievable, a compact fusion development programme, using smaller reactors operating at lower fusion power, would require smaller quantities of tritium than the ITER programme, leaving sufficient tritium available for multiple concepts to be developed concurrently. The development of concurrent fusion concepts increases the chances of success, as it spreads the risk of failure. Additionally, if full tritium breeding capability is not expected to be demonstrated in DEMO until after 2050, an opportunity exists for compact fusion programmes to incorporate tritium breeding technology in nearer-term devices. DD start-up, which avoids the need for external tritium for reactor start-up, is dependent upon full tritium breeding capability, and may be essential for large-scale commercial roll-out of fusion energy. As such, from the standpoint of availability and use of external tritium, a compact route to fusion energy may be more advantageous, as it avoids longer-term complications and uncertainties in the future supply of tritium