My child/children won't be attending school today as they are not feeling well
My child will not be coming to school today as they are unwell
My child will be absent today as they are not feeling well/are unwell
When talking about someone not going somewhere then we used the terms 'won't be attending' 'will not be coming' or 'will be absent'
when explaining why as they are ill then you can say as they are 'ill', 'not feeling well' or 'unwell'
人がどこかに行かないことは、
'won't be attending'（行かない）や、
'will not be coming'（行かない）
'will be absent'（[欠席する](https://eikaiwa.dmm.com/uknow/questions/63506/)）
で表せます。
「具合が悪い」と行くことのできない理由を説明したいなら、
'ill'（病気で）や、
'not feeling well'（[体調が良くない](https://eikaiwa.dmm.com/uknow/questions/39317/)）
'unwell'（体調が良くない）
が使えます。
My child/children won't be attending school today as they are not feeling well
私の子供は具合が悪いので今日は学校を休みます。
My child will not be coming to school today as they are unwell
私の子供は具合が悪いので今日は学校を休みます。
My child will be absent today as they are not feeling well/are unwell
私の子供は具合が悪いので今日は学校を休みます。
My children won't be at school today because they are not feeling well.
My children cannot make it to school today since there is something going on in their lives.
1文目は病気や風邪でお休みを伝える場合の表現です。
2文目は[私用](https://eikaiwa.dmm.com/uknow/questions/42646/)でお休みを伝える場合の表現です。
※make it to～は～に[出席する](https://eikaiwa.dmm.com/uknow/questions/62511/)という意味です。
※there is something going on in one's lifeは休まなければならないという旨を抽象的に伝える際の言い方です。私用の場合はこちらが使えるかと思い、紹介いたしました。
お役に立てれば幸いです。
My child will not be attending school today because he/she is sick.
My child will be absent from school today because he/she is unwell.
Since you are informing the school well before the classes begin at his/her school, the appropriate thing to do is to use the future verb tense expression, 'will not be'. The verb to 'attend' in this conetxt means to 'be present at a particular place or event', in this case, at school. The verb 'absent' means 'not present' in this context. When someone is 'sick' or 'unwell', it means that the person's body has been affected by an illness.
So you may say:
My child will not be attending school today because he/she is sick.
or
My child will be absent from school today because he/she is unwell.
授業が始まるずっと前に学校に伝えるわけなので、ここでは 'will not be' という未来表現を用いるのが適切です。動詞の
'attend' はこの文脈では「（学校に）出席する」の意味です。
'absent'はここでは 'not present'（欠席している）という意味です。
'sick' あるいは 'unwell' は「病気で体調が悪い」という意味です。
次のように言えます。
My child will not be attending school today because he/she is sick.（子どもが今日は体調が悪いので学校を休みます）
My child will be absent from school today because he/she is unwell.（子どもが今日は体調が悪いので学校を休みます）
My child is sick and will not be attending school today!
My child is sick and will not be coming to school today!
My child is sick and will be absent today!
When we want to explain that we will not be going somewhere, then we use words like "coming" or "attending" or "absent".
"My child is sick and will not be attending school today!"
"My child is sick and will not be coming to school today!"
"My child is sick and will be absent today!"
どこかに行かないことは、 "coming" "attending" "absent" などを使って説明できます。
"My child is sick and will not be attending school today!"
"My child is sick and will not be coming to school today!"
"My child is sick and will be absent today!"
（子どもが風邪を引いたので今日は学校を休みます）
My child won't be coming in for school today: My child won't be attending school today.
My child is ill: My child is not feeling well.
"My child won't be coming in for school today.'
This means that the child will not be attending school today.
The reasons could be many, the child may be ill or the parents may not be able to bring the child in for different reasons.
"My child won't be coming in for school today.'（子どもが今日学校を休みます）
これは「子どもは今日学校を欠席する」という意味です。
理由はいろいろです。例えば子どもが病気ということもあるでしょうし、親が何かの理由で子どもを学校に連れてこられないということもあるかもしれません。
(name) won't be able to make it in today, unfortunately (they) have (has) a fever/cold/chicken pox.
(name) has got an appointment at the (doctors/dentists) & needs to have the day off.
(name) will be absent from school today, we have some personal issues. (can be used for emergencies)
In the UK, it can be a nightmare trying to arrange time off school for kids. Generally, schools require an explanation as to why the child is absent. You would normally say this in the third person, or, talking about that child.
For illness you could use:
"John won't be able to make it in today, unfortunately, he has chicken pox".
"John & Mary won't be able to make it in today, unfortunately, they both have a fever".
For appointments/meetings you could use:
"John has got an appointment at the hospital & needs to have the day off".
"Mary has got an appointment at the dentist on Friday & needs to have the afternoon off".
For personal issues you could use:
"Mary will be absent from school today, we have some personal issues. Sadly, her goldfish passed away".
"John will be absent from school today, we have some private matters."
"Mary will be absent from school on Friday. We are travelling to Scotland to see the Loch Ness Monster".
イギリスでは、子どもの学校の休みを調整するのは悪夢のような経験になる可能性があります。たいてい学校はなぜ子どもが休むのかの説明を求めます。普通これは第三者の立場で、つまりその子どもについて話しますね。
病気のときには次のように言えます。
"John won't be able to make it in today, unfortunately, he has chicken pox".（ジョンは今日は学校に行けません。残念ながら水ぼうそうになりました）
"John & Mary won't be able to make it in today, unfortunately, they both have a fever".（ジョンとメアリーは今日は学校に行けません。残念ながら二人とも熱があります）
予約があるときには次のように言えます。
"John has got an appointment at the hospital & needs to have the day off".（ジョンは病院の予約があるので学校を休まないといけません）
"Mary has got an appointment at the dentist on Friday & needs to have the afternoon off".（メアリーは金曜日歯医者の予約があるので、午後休まないといけません）
個人的な理由なら次のように言えます。
"John will be absent from school today, we have some private matters."（今日は私的な用事があるのでジョンは学校を休ませていただきます）
"Mary will be absent from school on Friday. We are travelling to Scotland to see the Loch Ness Monster".（メアリーは金曜日に学校を休ませていただきます。ネッシーを見にスコットランドに旅行に行きます）
Today my child will have to take the day off school
My child will unfortunately have to take a sick day today
Due to not feeling well my child will have to take the day off
these three casual phrases of telling/asking if the child can 'take the day off' (not do a something i.e school or work)
sick day is also used to describe not going to work or school and staying at home
子どもが学校を欠席することを伝える／欠席してもいいかどうかを確認するカジュアルな3通りの言い方です。
take the day off = 学校や仕事を休む
'sick day' も、仕事や学校を休み、家にいることを表します。
イギリス 
日本 
南アフリカ 
