Baseclass inheritance results in Exception

[Jawz84]

Throws exception:

class Person {[int]$age ; Person($a) {$this.age = $a}}; class Child : Person {[string]$School   ;   Child([int]$a, [string]$s ) : base($a) {         $this.School = $s     } }

#log:
[2021-06-12T19:46:13.911Z] PowerShell code sent: class Person {[int]$age ; Person($a) {$this.age = $a}}; class Child : Person {[string]$School   ;   Child([int]$a, [string]$s ) : base($a) {         $this.School = $s     } }
[2021-06-12T19:46:13.934Z] error
[2021-06-12T19:46:13.934Z] explainpowershell: Object reference not set to an instance of an object.
[2021-06-12T19:46:13.936Z] Executed 'SyntaxAnalyzer' (Succeeded, Id=81cd567f-89e4-4054-a6c6-4389f5f28c51, Duration=32ms)