MCAS values not shown correctly on charts

[kevinrobinson]

This has two parts.

With summary charts

Single data points for recent scaled scores don't show up on the sparkline chart, even though they show on the numeric value, and they show on the chart below. As a guess, this may be because it's a single data point or because it's for Next Gen MCAS. Somerville test case: student_id: 1126, probably impacts NB too.

Next Gen SGP values don't show on more details charst

It looks like Next Gen MCAS SGPs don't show up in chart, despite being in the database and it's because of read-side bugs, starting in StudentProfileChart.rb and into the UI code. Somerville test case: student_id: 1126, student_assessment_id: 124584, and this probably impacts NB too.

[kevinrobinson]

Somewhat related, about validations on these values: #1941